Distinguished Lecturer Program


The IEEE AP-S Distinguished Lecturer Program provides AP-S chapters around the world with talks by experts on topics of interest and importance to the AP community. The chapters incur little or no cost in making use of this program. Each chapter can request a maximum of two visits per year by our Distinguished Lecturers (DLs). (One of the two visitors is allowed to be a former Distinguished Lecturer, if the chapter prefers.) Requests must be approved prior to making an official commitment by contacting the Chair of the Distinguished Lecturer Program. The AP-S Society will normally reimburse Distinguished Lecturers up to $1,250 for presentations to AP-S Chapters located inside the DL's IEEE geographic region. Travelling outside the DL’s geographic region is currently reimbursable at up to $2,500. (One exception is that Canada and the U.S. are considered as one region for reimbursement purposes.) Each additional chapter visited on the same trip, within the same geographical region, is normally reimbursable at the rate of $1,250. Exceptions to the above reimbursement limits require approval from the Chair of the Distinguished Lecturer Program. To receive reimbursement, the lecturers are required to keep all expense receipts and send them electronically to the AP-S Secretary/Treasurer along with an expense report on a standard IEEE reimbursement form, which is available from the Chair of the Distinguished Lecturer Program.

 

All Distinguished Lecturers are outstanding in their fields of specialty. Collectively, the Distinguished Lecturers possess a broad range of expertise within the area of AP. Thus, the chapters are strongly encouraged to use this program as a means to make their local AP community aware of the most recent scientific and technological trends.

 

Although the Chair selects and appoints the Distinguished Lecturers, the Chair is open to suggestions from members of the IEEE AP-S and the AP Chapter Chairs for the selection of appropriate topics and/or the nomination of future Distinguished Lecturers, and suggestions are welcome. The Distinguished Lecturer Program Handbook can be found here.

 

 

 

The Chair of the Distinguished Lecturer Program is

 

Dr. David Jackson
Department of ECE
N308 Engineering Bldg. 1
University of Houston
Houston, TX 77204-4005
Telephone: 713-743-4426 (office)
Fax: 713-743-4444
djackson@uh.edu


AP-S Distinguished Lecture Appointments

 

 

2007-2010
Koichi Ito

 

2009-2011
Nick Buris
Zhi Ning Chen
Werner Wiesbeck

 

2010-2012
Marta Martínez Vázquez
Roberto Graglia

 

2011-2013
Arun Bhattacharyya
Jean-Charles Bolomey
Levent Gurel
Per-Simon Kildal
Jin-Fa Lee
Joshua Li
Sembiam Rengarajan
Tapan Sarkar

 

 

2012-2014

Kwok Wa (Ben) Leung

Stefano Maci

Brian Kent

Monai Krairiksh

Yahia Antar

 

2013-2015

Ari Sihvola

Mats Gustafsson

Ahmed Kishk


 

2007-2011

 

 

Koichi Ito
Prof. Koichi Ito
Department of Medical System Engineering
Graduate School of Engineering
Chiba University
1-33 Yayoi-cho, Inage-ku, Chiba-shi, 263-8522
Japan
k-ito@ieee.org

Koichi Ito was born in Nagoya, Japan and received the B.S. and M.S. degrees from Chiba University, Chiba, Japan, in 1974 and 1976, respectively, and the D.E. degree from Tokyo Institute of Technology, Tokyo, Japan, in 1985, all in electrical engineering. From 1976 to 1979, he was a Research Associate at the Tokyo Institute of Technology. From 1979 to 1989, he was a Research Associate at Chiba University. From 1989 to 1997, he was an Associate Professor at the Department of Electrical and Electronics Engineering, Chiba University, and is currently a Professor at the Department of Medical System Engineering, Chiba University. From 2005 to 2009, he was Deputy Vice-President for Research, Chiba University. From 2008 to 2009, he was Vice-Dean of the Graduate School of Engineering, Chiba University. Since April 2009, he has been appointed as Director of Research Center for Frontier Medical Engineering, Chiba University. In 1989, 1994, and 1998, he visited the University of Rennes I, France, as an Invited Professor. He has been appointed as Adjunct Professor to the University of Indonesia since 2010.

 

His main research interests include analysis and design of printed antennas and small antennas for mobile communications, research on evaluation of the interaction between electromagnetic fields and the human body by use of numerical and experimental phantoms, microwave antennas for medical applications such as cancer treatment, and antenna systems for body-centric wireless communications.

Professor Ito is a Fellow of the IEEE, a Fellow of the IEICE and a member of AAAS, the Bioelectromagnetics Society (BEMS), the Institute of Image Information and Television Engineers of Japan (ITE) and the Japanese Society for Thermal Medicine. He served as Chair of the Technical Group on Radio and Optical Transmissions, ITE from 1997 to 2001, Chair of the Technical Committee on Human Phantoms for Electromagnetics, IEICE from 1998 to 2006, Chair of the IEEE AP-S Japan Chapter from 2001 to 2002, General Chair of the 2008 IEEE International Workshop on Antenna Technology (iWAT2008), an AdCom member for the IEEE AP-S from 2007 to 2009, and an Associate Editor for the IEEE Transactions on Antennas and Propagation from 2004 to 2010. He currently serves as a Distinguished Lecturer for the IEEE AP-S and Chair of the Technical Committee on Antennas and Propagation, IEICE. He has been appointed as General Chair of the 2012 International Symposium on Antennas and Propagation (ISAP2012) to be held in Nagoya, Japan, a member of the Board of Directors, BEMS, a Councilor to the Asian Society of Hyperthermic Oncology (ASHO), and Chair of the IEEE AP-S Committee on Man and Radiation (COMAR).

 

Antennas for Body-Centric Wireless Communications


Recently, a study on body-centric wireless communications has become an active and attractive area of research because of their various applications such as e-healthcare, support systems for specialized occupations, monitoring systems for elderly and handicapped people, entertainment, and so on. Whereas UHF bands are subjects of interest especially in Europe and USA, HF bands are of great interest especially in Japan. Hence, all of the prospective frequencies are in an extremely wide range, and an objective idea on how to select a right frequency band for individual applications is required. As for the antennas, many types of wearable (on-body) and implantable (in-body) antennas have been reported.

 

Currently in our laboratory, we have been studying on frequency dependence of basic characteristics of simple wearable antennas as well as body-centric wireless communication channels in the range of HF to UHF (3 MHz – 3 GHz). Also, we have been investigating numerically and experimentally thin implantable antennas in UHF band.

 

In this presentation, firstly, electric field distributions around the human body wearing a small top-loaded monopole antenna are numerically calculated and compared in a wide range of HF to UHF bands. Then, received open voltages at receiving antennas which are equipped at several different points on the human body are numerically investigated. The received open voltages are also numerically calculated and compared with several different postures of the human body. Finally, some basic performances of miniaturized thin implantable antennas are numerically calculated in UHF band. Experimental validation is also demonstrated.


Microwave Antennas for Medical Applications


In recent years, various types of medical applications of antennas have widely been investigated and reported. Typical recent applications are:

 

(1) Information transmission:
- RFID (Radio Frequency Identification) / Wearable or Implantable monitor
- Wireless telemedicine / Mobile health system

 

(2) Diagnosis:
- MRI (Magnetic Resonance Imaging) / fMRI
- Microwave CT (Computed Tomography) / Radiometry

 

(3) Treatment:
- Thermal therapy (Hyperthermia, ablation, etc)
- Microwave knife

 

In this presentation, three different types of antennas which have been studied in our laboratory are introduced. Firstly, a pretty small antenna for an implantable monitoring system is presented. A cavity slot antenna is a good candidate for such a system. Some numerical and experimental characteristics of the antenna are demonstrated. Secondly, some different antennas or “RF coils” for MRI systems are introduced. In addition, SAR (specific absorption rate) distributions in the abdomen of a pregnant woman generated in a bird cage coil are illustrated. Finally, after a brief overview of thermal therapy and microwave heating, coaxial-slot antennas and array applicators composed of several coaxial-slot antennas for minimally invasive microwave thermal therapies are introduced. Then a few results of actual clinical trials by use of coaxial-slot antennas are demonstrated from a technical point of view. Other therapeutic applications of the coaxial-slot antennas such as hyperthermic treatment for brain tumor and intracavitary hyperthermia for bile duct carcinoma are introduced.

 


2009-2011

 

Dr. Nicholas E. Buris
President
NEBENS
Deer Park, IL
nick.buris@nebens.com

 

Nick Buris received the diploma of Electrical Engineering in 1982 from the National Technical University of Athens, Greece and the Ph.D. in EE from the North Carolina State University, in 1986 working on microwave propagation in inhomogeneous thin ferrite films.. In 1986, he was a visiting professor at NCSU working on space reflector antennas for NASA. In 1987 he joined the faculty of the ECE dept. at UMass, Amherst. His research work there focused on microwave magnetics, phased arrays printed on dielectric and ferrite substrates and broadband antennas. In the summer of 1990 he was a faculty fellow at the NASA Langley Research Center working on calibration techniques for dielectric measurements and an ionization (plasma) sensor for an experimental reentry spacecraft. In 1992 he joined the Applied Technology organization of Motorola’s Paging Product Group and in 1995 he moved to Corporate Research to start an advanced modeling effort. At Motorola he was until recently a director, managing large projects on antenna product design, rf propagation measurements, RFID’s, mm waves and the development of proprietary software tools for electromagnetic and system design and optimization. In 2009 he founded NEBENS, a small company focusing on cross layer design aspects (antenna, coverage and algorithms) of Smart Antenna based wireless systems.


Nick is an IEEE fellow and a distinguished lecturer of the IEEE Antennas and Propagation society. He is a member of the IEEE Microwave Theory and Techniques technical program committee and has been member and chair of various IEEE and Telecommunications Industry Association (TIA) standards committees on antennas and RF exposure.

Cross-Layer Design of Smart Antenna Systems

Smart Antenna Systems use the additional degrees of freedom offered by their multiple antennas to exploit, among other things, multipath in the propagation environment. Therefore, by construction, antenna design of smart antenna systems cannot be assessed by simple performance metrics such as gain, polarization and efficiency alone. At a minimum, performance has to be considered in the context of the nature and degree of the multipath. Capacity, the maximum possible throughput, is an appropriate performance metric when the antennas are properly combined with their propagation environment but nothing more is known about the system. When, additionally, the specific Link and Media Access Control (MAC) layer characteristics of the system are taken into account, the actual throughput of the communication link becomes a more appropriate performance metric. A Cross-Layered design approach of Multiple Input Multiple Output (MIMO) antenna systems is presented in this talk. An electromagnetics exact formulation from baseband-to-baseband of a Smart Antenna System is given. The formulation consists of full wave analyses of the antenna arrays involved on both sides of the link and a plane wave decomposition for the propagation environment. Subsequently, the baseband signals are fed into link simulators, specific for each system of interest, to provide estimates of the Bit Error Rate (BER) and throughput. Calibration and Channel estimation algorithms are described for Time Division Duplex (TDD) systems, such as the IEEE 802.16 (WiMAX) and TDD LTE. The state of the art in designing antennas for terminals and for base stations is outlined. Examples of actual product designs for WiMAX and IEEE 802.11n are also given.

 

Finally, the talk ends with some recommendations on research topics to further the state of the art.


Electromagnetic Design for Wireless Applications and Multidisciplinary Optimization

This presentation starts with several specific electromagnetic design examples for wireless applications. These examples include antennas for cellular handsets, RFIDs as well as electromagnetic interference solution concepts. Various characteristics of advanced design methods are then examined. The case is made that multidisciplinary design methods need to be developed and employed for efficient solution of complex problems. At present, multidisciplinary issues encountered at the design of feature rich products are solved by intense communications between the design groups of interacting disciplines. The design of today’s challenging products demands the same and higher degree of communications between the tools used by interacting disciplines. An electromagnetic and structural design example of a cell phone drop to the floor (impact analysis) is used to elucidate the concepts discussed. Additionally, an outline of a framework capable of addressing concurrent optimization of multiple disciplines and of complex products is presented. The seminar ends with a list of proposed problems that need to be solved so that maximum efficiency can be achieved in solving the complex problems of the future.

 


 


Zhi Ning Chen

Institute for Infocomm Research
20 Science Park Road
#02-21/25 Teletech Park
Singapore 117674
chenzn@i2r.a-star.edu.sg and znchen@ieee.org

 

Dr Zhi Ning Chen received his BEng, MEng, and PhDs degrees all in Electrical Engineering from the Institute of Communications Engineering (ICE), China and University of Tsukuba, Japan, respectively. During 1988-1995, he worked at ICE as Lecturer and later Associate Professor, as well as at Southeast University, China as a Postdoctoral Fellow and later as an Associate Professor. During 1995-1997, he joined the City University of Hong Kong as a Research Assistant and later a Research Fellow. In 1997, he was awarded a JSPS Fellowship to conduct his research at the University of Tsukuba, Japan. In 2001 and 2004, he visited the University of Tsukuba under a JSPS Fellowship Program (senior level). In 2004, he worked at IBM T. J. Watson Research Center, USA as an Academic Visitor. Since 1999, he has worked with the Institute for Infocomm Research (formerly known as Center for Wireless Communications and the Institute for Communication Research) as Member of the Technical Staff (MTS), Principal MTS, Senior Scientist, and Lead Scientist. He is currently appointed as Principal Scientist and Department Head for RF & Optical and concurrently holds Visiting/Adjunct/Guest Professor appointments at Southeast University, Nanjing University, Shanghai Jiao Tong University, Tsinghua University, Tongji University, Dalian Maritime University, and the National University of Singapore. He was appointed as an Adjunct Professor/Associate Professor at Zhejiang University and Nanyang Technologies University.


Dr Chen has organized many international events as the general chair, technical program committee chair, and as a key member of organizing committees. He is the founder of the International Workshop on Antenna Technology (iWAT). He has published 290 journal and conference papers as well as authored and edited books entitled Broadband Planar Antennas, UWB Wireless Communication, Antennas for Portable Devices, and Antennas for Base Station in Wireless Communications. He also contributed to the books UWB Antennas and Propagation for Communications, Radar, and Imaging as well as Antenna Engineering Handbook. He is holding 25 granted and filed patents with 21 licensed deals with industry. He is the recipient of the CST University Publication Award 2008, IEEE AP-S Honorable Mention Student Paper Contest 2008, IES Prestigious Engineering Achievement Award 2006, I2R Quarterly Best Paper Award 2004, and IEEE iWAT 2005 Best Poster Award. His current research interest includes applied electromagnetics, antennas for applications of microwaves, mmW, submmW, and THz in communication and imaging systems. Dr Chen is a Fellow of the IEEE for his contribution to small and broadband antennas for wireless applications. (www1.i2r.a-star.edu.sg/~chenzn)

 

Miniaturization of Ultra-wideband Antennas

 

About the Talk: Ultra-wideband (UWB) has become the promising wireless technology in commercial applications such as next-generation short-range high-data-rate wireless communications, high resolution imaging, and high accuracy radar. The antenna is one of the key designs in UWB wireless systems. This talk starts with a brief introduction to design challenges of UWB antennas, followed by state-of-the-art solutions. Next, miniaturization technologies for UWB antennas are addressed. Planar designs are highlighted due to their unique merits and wide adoption in practical applications. First, a newly developed technique to achieve ground-independent UWB antenna performance, one of the most challenging issues in small antenna design, is addressed. A design example is used to elaborate the mechanism of the method. Based on this concept, an antenna with further reduced size is designed to fit wireless USB dongles. Furthermore, an innovative compact diversity UWB antenna shows the advantage of ground-independence for small antennas in diversity applications. Last, UWB antennas co-designed with filtering performance using bandpass/bandstop filters integrated into the antenna are proposed to reduce the overall size of devices and enhance antenna performance. At the end, the trends of UWB antenna R&D are discussed, correlated with applications and market demands.

 

Design Considerations of Antennas in MIMO Systems -from Antenna Engineering Perspectives

 

About the Talk: This talk will present and discuss the key design considerations for antennas in multiple-input-multiple-output (MIMO) wireless communication systems from antenna engineering perspectives. First, the effects of antenna design on diversity performance of MIMO systems will be analyzed. This will show that the configurations of the antennas can greatly affect system performance; in particular, the signal correlation at both the transmitters and the receivers in both the uplink and the downlink. Second, the effects on the envelope correlation and capacity of MIMO systems will be evaluated by using antenna parameters, namely S-parameters and radiated electric fields. In particular, the antenna efficiency that is affected by inter-element mutual coupling is taken into account in the antenna design. Third, the concepts of two-dimensional and three-dimensional envelope correlation coefficient distributions are introduced and discussed. As a result, the performance of MIMO systems, especially for pattern diversity, can be further optimized instead of using the conventional average envelope correlation coefficients. Fourth, the concept of overall correlation of the system is proposed to evaluate the diversity performance of MIMO systems, which will, for example, include spatial, polarization, and pattern diversity. After that, the design considerations for antennas in MIMO systems are presented from an antenna engineering point of view. Last, a compact three-element MIMO antenna system designed for indoor 2.4 GHz WLAN applications is exemplified to validate the design considerations proposed here. Moreover, the technology to reduce inter-element mutual coupling is also introduced and applied to the three-element design.

 

(Proposed): Antennas for RFID Tags and Readers

 

About the Talk: Radio frequency identification (RFID) technology has been rapidly developing in recent years and the applications have been widely found in service industries, distribution logistics, manufacturing companies, and product-flow systems. Antenna design for readers and tags is one of the key factors for RFID systems. The optimized tag and reader antenna design will benefit RFID systems with longer reading range, better detection accuracy, lower fabrication cost, and simple system configuration and implementation. This talk will start with a brief introduction to RFID systems, which may be active, passive, or semi-active systems, and operate at LF, HF, UHF, or MW bands. Then the key considerations related to the antenna design for tags and readers will be addressed from system perspectives. After that, case studies will highlight specific challenges for antennas in the HF near-field and UHF near/far-field systems. In particular, important engineering factors such as environmental effects vs. co-design methodology, size constraints, cost constraints, and UHF near-field reader antenna coverage will be presented with corresponding practical design cases.

 


 

Werner Wiesbeck
Prof. Dr.-Ing. Werner Wiesbeck
Inst. für Höchstfrequenztechnik und Elektronik
Universität Karlsruhe (TH)
Kaiserstr. 12
76131 Karlsruhe
werner.wiesbeck@ihe.uka.de

 

Werner Wiesbeck (SM 87, F 94) received the Dipl.-Ing. (M.S.E.E.) and the Dr.-Ing. (Ph.D.E.E.) degrees from the Technical University Munich in 1969 and 1972, respectively. From 1972 to 1983 he was with AEG-Telefunken in various positions including that of head of R&D of the Microwave Division in Flensburg and marketing director Receiver and Direction Finder Division, Ulm. During this period he had product responsibility for mm-wave radars, receivers, direction finders and electronic warfare systems. From 1983 to 2007 he was the Director of the Institut für Höchstfrequenztechnik und Elektronik (IHE) at the University of Karlsruhe (TH) and he is now Distinguished Scientist at the Karlsruhe Institute of Technology (KIT). Research topics include antennas, wave propagation, Radar, remote sensing, wireless communication and Ultra Wideband technologies. In 1989 and 1994, respectively, he spent a six months sabbatical at the Jet Propulsion Laboratory, Pasadena. He is a member of the IEEE GRS-S AdCom (1992-2000), Chairman of the GRS-S Awards Committee (1994 – 1998, 2002 - ), Executive Vice President IEEE GRS-S (1998-1999), President IEEE GRS-S (2000-2001), Associate Editor IEEE-AP Transactions (1996-1999), past Treasurer of the IEEE German Section (1987-1996, 2003-2007). He has been General Chairman of the ’88 Heinrich Hertz Centennial Symposium, the '93 Conference on Microwaves and Optics (MIOP '93), the Technical Chairman of International mm-Wave and Infrared Conference 2004, Chairman of the German Microwave Conference GeMIC 2006 and he has been a member of the scientific committees and TPCs of many conferences. For the Carl Cranz Series for Scientific Education he serves as a permanent lecturer for Radar systems engineering, wave propagation and mobile communication network planning. He is a member of an Advisory Committee of the EU - Joint Research Centre (Ispra/Italy), and he is an advisor to the German Research Council (DFG), to the Federal German Ministry for Research (BMBF) and to industry in Germany. He is the recipient of a number of awards, lately the IEEE Millennium Award, the IEEE GRS Distinguished Achievement Award, the Honorary Doctorate (Dr. h.c.) from the University Budapest/Hungary, the Honorary Doctorate (Dr.-Ing. E.h.) from the University Duisburg/Germany and the IEEE Electromagnetics Award 2008. He is a Fellow of IEEE, an Honorary Life Member of IEEE GRS-S, a Member of the IEEE Fellow Cmte, a Member of the Heidelberger Academy of Sciences and Humanities and a Member of the German Academy of Engineering and Technology (acatech).


3D Wave-Propagation Modeling for Mobile Communications (C2C, C2X)

 

For communications the knowledge of wave propagation is essential. The channel influences especially in mobile communications the total link characteristic more than the antennas. This lecture presents state of the art 3D wave propagation modeling and its application to mobile to mobile communications (C2C, V2V…). The inclusion of dynamic scenarios allows the so called “Virtual Drive”, a complete system simulation and iterative optimization, regarding antenna placement and characteristics on vehicles for Diversity and MIMO.


For the wave propagation a 3D ray-tracing tool, based on the theory of geometrical optics (GO) and the Uniform Theory of Diffraction (UTD), is used. The model includes modified Fresnel reflection coefficients for the reflection and the diffraction based on the UTD. Vehicles, carrying the antennas are electromagnetically modeled.

 

The propagation channels are characterized by delay spread, Doppler spread and angular spread for different situations. Dynamic simulations are illustrated by movies. The traffic scenarios are real world with multiple lanes, line of sight and non line of sight. The simulations are verified by measurements.

 

Dynamic wave propagation simulations in real world scenarios are only since a few years possible. They may revolutionize the design and integration of antennas in cars, trains, military vehicles and so on. The computer based “Virtual Drive” may save time and avoid misleading developments.


UWB Antennas and Channel Characteristics


Spectrum is presently one of the most valuable goods worldwide as the demand is permanently increasing and it can be traded only locally. Since the United States FCC has opened the spectrum from 3.1 GHz to 10.6 GHz, i.e. a bandwidth of 7.5 GHz, for unlicensed use with up to –41.25 dBm/MHz EIRP, numerous applications in communications and sensor areas are showing up. All these applications have in common that they spread the necessary energy over a wide frequency range in this unlicensed band in order to radiate below the limit. The results are ultra wideband systems. These new devices exhibit quite surprising behavior, especially at the air-antenna interface. This talk presents an insight into design, evaluation and measurement procedures for Ultra Wide Band (UWB) antennas as well as into the characteristics of the UWB radio channel as a whole. UWB antenna basics and principles of wideband radiators, transient antenna characterization and UWB antenna quality measures, derived from the antenna impulse response, are topics. EM simulations and measurements of transient antenna properties in frequency domain and in time domain are included. Different antennas, based on different UWB principles, will be presented. Depending on the interest there are: ridged horn antenna, Vivaldi antenna, logarithmic periodic antenna, mono cone antenna, spiral antenna, aperture coupled bowtie antennas, multimode antennas, sinus antenna and impulse radiating antennas. The channel characterization comprises ray-tracing tools for deterministic indoor UWB channel modeling and measurements. The advantages and drawbacks of the UWB transmission will be discussed, depending on interest. The radiation from different antennas will be demonstrated by movies with a pulse excitation.

 


2010-2012

 

Marta Martínez-Vázquez
Dr. Marta Martínez Vázquez
Department of Antennas & EM Modelling
IMST GmbH
Carl-Friedrich-Gauss-Str. 2-4
47475 Kamp-Lintfort
Germany
martinez@imst.de

 

Marta Martínez-Vázquez was born in Santiago de Compostela, Spain, in 1973. She obtained the Dipl.-Ing. in telecommunications and Ph.D. degree from Universidad Politécnica de Valencia, Spain, in 1997 and 2003, respectively. In 1999 she obtained a fellowship from the Pedro Barrié de la Maza Foundation for postgraduate research at IMST GmbH, in Germany. Since 2000, she is a full-time staff member of the Antennas and EM Modelling department of IMST. Her research interests include the design and applications of antennas for mobile communications, planar arrays and radar sensors, as well as Electromagnetic Bandgap (EBG) materials. Dr. Martínez-Vázquez was awarded the 2004 "Premio Extraordinario de Tesis Doctoral" (Best Ph.D. award) of the Universidad Politécnica de Valencia for her dissertation on small multiband antennas for handheld terminals. She has been a member of the Executive Board of the ACE (Antennas Centre of Excellence) Network of Excellence (2004-2007) and the leader of its activity on small antennas. She is the vice-chair of the COST IC0306 Action “Antenna Sensors and Systems for Information Society Technologies”, and a member of the IEEE Antennas and Propagation Society and of the Technical Advisory Panel for the Antennas and Propagation Professional Network of IET. She is the author of over 50 papers in journals and conference proceedings. Dr. Martínez-Vázquez’s career is an example of the positive results of such coordination programs. She started as an expert participant in COST 260, became a Working Group leader in COST 284, and a member of the Executive Board of ACA, leading the “Small Antennas” activity. Presently, she is the Vice-chair of the COST IC0603 Action.

 

Challenges in practical design of planar arrays

 

The development of new multimedia services and intelligent sensor systems is progressing at a rapid pace and requires the use of agile antenna frontends that are compact, highly efficient and cost-effective. These antennas are rarely off-the-shelf solutions. On the contrary, custom-tailored solutions are usually required in order to optimise the performance, and facilitate the integration into the final product.


In many applications, the best compromise for an antenna solution with respect to cost and performance is a planar array. In general, a planar array can be defined as an antenna in which all of the elements are situated in one plane. The antenna elements themselves can be patches or other planar or buried structures. The range of applications of planar arrays include agile RF-frontends for mobile satellite terminals, radar systems for automotive and security applications, and millimetre wave point-to-point or point-to-multipoint radio links for multimedia wireless networks.


Real-life communications systems can include antenna arrays with only a limited number of transmitters and receivers as well as very large arrays with hundreds of receive and transmit channels. A skilful symbiosis of industrial development and innovative research projects is the key to provide cost-effective products. Some typical applications will be described in the next sections.


Considerable experience is required for the design and realisation of planar antenna arrays at microwave frequencies, especially when broadband solutions are demanded. It is not only necessary to develop innovative concepts beyond the standard patch design, but it also becomes unavoidable to cope with material and manufacturing tolerances when realising the antennas on soft and hard substrates. Special care has also to be invested in the RF-feeding network and the transition between antenna and RF-circuitry, as the latter can become a bottleneck at high frequencies, hence limiting the available bandwidth.


In order to provide cutting-edge solutions, it is important not only to develop systems based on state-of-the art antenna concepts. Fast and highly accurate EM solvers are indispensable tools to simulate the whole antenna system. Access to prototyping tools and accurate measurement facilities are also required. The seamless integration of all these services helps reduce the number of iterations to obtain high-performance antennas, thus leading to reduced development time. A complete, industrial solution for complex planar arrays must cover the whole development chain, starting with the conceptual design and the development of new concepts and solutions, going through the prototyping and optimisation process, including antenna characterisation and diagnosis, up to the preparation of line production and qualification phase. Some of the key steps will be discussed in this talk.


An overview of European cooperation on antenna research


Antenna research has a long tradition in Europe, although the efforts have been often scattered and uncoordinated, with a large gap between university research and industrial applications. A first step towards collaborative research was made with the creation of the COST activities, also referred to as an Action (“CO-operation in the field of Scientific and Technological research”), sponsored by the European Commission. Under the COST umbrella, different Actions were approved since the early 1970s that deal with antenna R&D. From the first COST Action 25/1 ("Aerial Networks with Phase Control", 1973-1979) to the recently started COST IC 0603 Action (“Antenna Systems & Sensors for Information Society Technologies”, 2007-2011), the number of signatory countries has increased from 5 to over 20. These COST Actions have allowed the exchange of know-how in a non-competitive manner, and are still an excellent forum for open discussion regarding blue sky research. They have also fostered collaborations between European organizations and the mobility of researchers, especially young PhD students, through short term missions, for example. Being essentially an open forum at a pre-competitive level, COST is the ideal complement for other joint European research programs, and many innovative concepts and novel antenna designs have their roots in COST meetings.

 

Within the 6th Framework Program of the European Commission, a new structuring instrument was used to complement and enhance the collaboration initiated within COST, and thus further coordinate antenna research to deal with the new challenges of the 21st century: The Antenna Centre of Excellence (ACE) was established as a Network of Excellence, including over 50 European institutions, both industrial and academic from 17 European countries, with over 300 researchers and 130 PhD students, and over 100 external participants from around the world as members of the ACE Community”. Over 4 years, ACE has tried to structure the fragmented European antenna R&D world, reduce duplications and boost excellence and competitiveness in key areas. Some of the results of ACE are:

 

  • The creation of the European School of Antennas, a new system of geographically distributed PhD school which aims to improve the antenna advanced training and research in Europe
  • Cooperation in antenna measurement, with an on-line database of measurement facilities and collaboration agreements
  • Benchmarking of measurement facilities and software tools
  • The development of the EDI (Electromagnetic Data Interface) for the exchange of compatible data between different software tools
  • The creation of EuCAP (European Conference on Antennas and Propagation), EurAAP (European Association on Antennas And Propagation) and many new research groupings in critical areas
  • The Virtual Centre of Excellence, a multimedia platform designed to provide a set of added value services to this Community by establishing a single point (website based) to share information across the entire research-manufacturing-users chain.

 

Terminal antenna design: practical considerations

 

Nowadays, the access to mobile communications not only through mobile telephones, but also other kind of portable devices such as notebooks or PDAs, equipped with PCMCIA cards, allows providing almost universal connectivity, with access to public or private networks. Therefore, both cellular standards, such as the GSM family and third generation standards such as UMTS, as well as unlicensed networks, like WLAN, should be accessible with a single device. However, the limited space foreseen for the antenna and the small overall size of the terminal are often the reason of the narrow band characteristics of the resulting antennas. This problem becomes even more serious when a multiband or an ultra-wideband antenna has to be designed. Also, only a careful design of the antenna taking into account the interaction both with the handset components and the human user can lead to satisfying solutions that fulfill the given requirements for mobile communications handsets. Their design is, however, no trivial task due not only to the extensive requirements of modern antennas but also to plethora of physical factors that impinge on their performance, such as the close proximity of electronic components.

 

However, in the design of antennas for commercial applications, the designer has to take into account many issues not directly related to the antenna itself. Antenna engineers have to interact with other departments, to satisfy all the requirements in terms of, for example, mechanical stability, aesthetical design or compliance testing. Thus, the design must be able to adapt the antenna concept to eventual changes in the device or the specifications. Although the use of powerful software packages has allowed one to precisely simulate the antennas in such a complex environment, they are useless without an in-depth knowledge of electromagnetic theory and experience in solving such problems.


Dr. Martínez-Vázquez has been involved in the design of antennas for mobile communications both from the academic and the industrial point of view, which allows her to have a global view on the problems related to this topic.

 

 


 

 

Roberto D. Graglia
Politecnico di Torino
Dipartimento di Elettronica
Corso Duca degli Abruzzi 24
10129 Torino
ITALY
roberto.graglia@polito.it

 

Roberto D. Graglia was born in Turin, Italy, in 1955. He received the Laurea degree (summa cum laude) in electronic engineering from the Polytechnic of Turin in 1979, and the Ph.D. degree in electrical engineering and computer science from the University of Illinois at Chicago in 1983. From 1980 to 1981, he was a Research Engineer at CSELT, Italy, where he conducted research on microstrip circuits. From 1981 to 1983, he was a Teaching and Research Assistant at the University of Illinois at Chicago. From 1985 to 1992, he was a Researcher with the Italian National Research Council (CNR), where he supervised international research projects. In 1991 and 1993, he was Associate Visiting Professor at the University of Illinois at Chicago. In 1992, he joined the Department of Electronics, Polytechnic of Turin, as an Associate Professor. He has been a Professor of Electrical Engineering at that Department since 1999. He has authored over 150 publications in international scientific journals and symposia proceedings. His areas of interest comprise numerical methods for high- and low-frequency electromagnetics, theoretical and computational aspects of scattering and interactions with complex media, waveguides, antennas, electromagnetic compatibility, and low-frequency phenomena. He has organized and offered several short courses in these areas. Prof. Graglia has been a Member of the editorial board of ELECTROMAGNETICS since 1997. He is a past associate editor of the IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION and of the IEEE TRANSACTIONS ON ELECTROMAGNETIC COMPATIBILITY. He is currently an associate editor of the IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS. He was the Guest Editor of a special issue on Advanced Numerical Techniques in Electromagnetics for the IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION in March 1997. He has been Invited Convener at URSI General Assemblies for special sessions on Field and Waves (1996), Electromagnetic Metrology (1999), and Computational Electromagnetics (1999). He served the International Union of Radio Science (URSI) for the triennial International Symposia on Electromagnetic Theory as organizer of the Special Session on Electromagnetic Compatibility in 1998 and was the co-organizer of the special session on Numerical Methods in 2004. Dr. Graglia served the IEEE Antennas and Propagation Society as a member of its Administrative Committee (AdCom), for the triennium 2006-2008. Since 1999, he has been the General Chairperson of the biennial International Conference on Electromagnetics in Advanced Applications (ICEAA), held in Turin. Prof. Graglia was elected Fellow of the IEEE in 1998 for his contributions in the application of numerical techniques in the studies of electromagnetic structures.

 

Computational Electromagnetics in the Frequency Domain


Finite methods are nowadays widely used for the analysis and design of complex electromagnetic structures. Among these methods, the Method of Moments is the most popular numerical technique for solving electromagnetic problems formulated in terms of integral equations, whereas the Finite Element and the Finite Difference methods are used to model problems in terms of differential equations. These methods share common features, have complementary advantages and, in advanced applications, they are often used in combination, possibly enriched by exact or asymptotic solutions of appropriate canonical problems. These numerical techniques have applications to many practical problems, e.g.: EMC & EMP; shielding radiation from printed circuits; microwave hazards; electromagnetic radiation from and penetration into vehicles, aircraft, ships; antennas near ground; design of frequency selective surfaces; radar scattering; etc. This presentation is intended to provide an in-depth coverage of the Moment Method and of the Finite Element and Finite Difference Methods, with discussion of absorbing boundary conditions and of hybrid methods. Particular applications can be considered in detail, such as problems involving nonlinear and/or anisotropic materials, as well as complex geometries. Dr. Graglia would like to keep this presentation quite broad, with the understanding that he will be coordinating its duration and specific focus with the inviting institutions.


Higher order modeling for Computational Electromagnetics


The progress in the area of Computational Electromagnetics, together with the cost reduction and continuous increase of the computational speed and power of modern computers, have contributed to the development and broad diffusion of numerical software for the analysis and design of complex electromagnetic structures and systems. The geometry and the materials of these structures can nowadays be modeled by powerful pre-processor codes able to provide high order description of the problem to the electromagnetic “solver-software”. To take advantage of the high quality models available by using the modern pre-processors, several researchers have also developed in the last decade high order basis functions for finite electromagnetic solver codes. This presentation is intended to provide an overview of the most recent developments obtained in this special area. After a brief overview of the fundamentals of finite methods, an in-depth coverage of higher order models for Moment Method and Finite Element Method applications is provided, thereby considering interpolatory and hierarchical higher order vector bases with a detailed discussion of the implementation problems and of the advantages provided by use of higher-order models. Dr. Graglia suggests this presentation to follow that entitled “Computational Electromagnetics in the Frequency Domain,” with the understanding that he will be coordinating with the inviting institutions for the streamlining of the presentation(s) according to their interests.

 

(modified: 29-Jun-2009)



 

2011-2013

 

Dr. Arun K. Bhattacharyya
Northrop Grumman Corporation
Redondo Beach, CA 90278.
Arun.bhattacharyya@ngc.com

 

Arun K. Bhattacharyya received his B.Eng. degree in electronics and telecommunication engineering from Bengal Engineering College, University of Calcutta in 1980, and the M.Tech. and Ph.D. degrees from Indian Institute of Technology, Kharagpur, India, in 1982 and 1985, respectively.

From November 1985 to April 1987, he was with the University of Manitoba, Canada, as a Postdoctoral Fellow in the electrical engineering department. From May 1987 to October 1987, he worked for Til-Tek Limited, Kemptville, Ontario, Canada as a senior antenna engineer. In October 1987, he joined the University of Saskatchewan, Canada as an assistant professor of electrical engineering department and then promoted to the associate professor rank in 1990. In July 1991 he joined Boeing Satellite Systems (formerly Hughes Space and Communications), Los Angeles as a senior staff engineer, and then promoted to scientist and senior scientist ranks in 1994 and 1998, respectively. Dr. Bhattacharyya became a Technical Fellow of Boeing in 2002. In September 2003 he joined Northrop Grumman Space Technology group as a staff scientist, senior grade. He became a Distinguished Engineer which is a very rare and honorable recognition in Northrop Grumman. He is the author of “Electromagnetic Fields in Multilayered Structures-Theory and Applications”, Artech House, Norwood, MA, 1994 and “Phased Array Antennas, Floquet Analysis, Synthesis, BFNs and Active Array Systems”, Hoboken, Wiley, 2006. He authored over 95 technical papers and has 15 issued patents. His technical interests include electromagnetics, printed antennas, multilayered structures, active phased arrays and modeling of microwave components and circuits.

Dr. Bhattacharyya became a Fellow of IEEE in 2002. He is a recipient of numerous awards including the 1996 Hughes Technical Excellence Award, 2002 Boeing Special Invention Award for his invention of High Efficiency horns, 2003 Boeing Satellite Systems Patent Awards and 2005 Tim Hannemann Annual Quality Award, Northrop Grumman Space Technology.

 

Floquet modal based Analysis of Finite and Infinite Phased Array Antennas


In this talk we present the Floquet modal analysis procedure for analyzing periodic array structures. The talk begins with a discussion on the relevance of Floquet analysis with regard to a scanned beam array design. Effects of mutual coupling on the performance of an array are discussed in details. It is shown how Floquet analysis can be employed to analyze a finite array with arbitrary amplitude taper including mutual coupling effects. A step-by-step procedure for aperture design is presented next. Method of analysis for an “array of subarrays” is also discussed. Design examples of patch and horn arrays are presented. A methodology for analyzing multilayered array structures with different periodicities is presented and applications of such structures in phased array antennas are discussed. In particular, characteristic features of a patch array loaded with a multilayered meander line polarizer are shown.


Efficient Shaped Beam Synthesis in Phased Arrays and Reflectors


Shaped beam array synthesis invites considerable attentions because arrays offer in-orbit reconfigurability, which is an attractive feature for communication and broadcasting satellites. In this talk, we present a brief overview of commonly used beam shaping algorithms. This is followed by the Projection Matrix Method of synthesis. The Projection Matrix method relies on orthogonal projection of the desired far field intensity vector onto the space spanned by the far field intensity vectors of the array elements. It is found that for a uniform convergence of the solution the far field sample space must be extended beyond the coverage region, otherwise the projection matrix becomes ill-conditioned. A general guideline for the far field sample space is provided. The method, with necessary amendments, is then employed successfully for a reflector surface synthesis. The method is found to be several times faster than the gradient search method commonly used for beam synthesis. Numerical results for array and shaped reflector syntheses are shown and the advantages are discussed.


Advanced Horn structures for Reflectors and Phased Arrays


In this talk we present an overview of various types of feed horns that are commonly used in single and multi-beam reflector systems and direct radiating arrays. The presentation begins with a discussion of smooth wall horns with single and multiple apertures, their operating principles, applications, advantages and their design procedures. In particular, the high aperture efficiency horns, both for rectangular and circular versions are discussed. The modal contents and generation of appropriate modes for achieving high aperture efficiency is presented. Potential applications of such horns in phased arrays and multi-beam reflectors are shown. Next, multiband horn structures using coaxial configuration and their applications are presented. This is followed by a presentation of various types of corrugated horns and their radiation characteristics. It is found that high Q resonances may occur in a corrugated horn within certain frequency bands where space wave and surface wave modes simultaneously propagate. A simple model is presented to demonstrate the resonance mechanism. Such resonances deteriorate the gain and cross-polar performances of a corrugated horn even if the return losses are acceptable at some resonant frequencies. Rectangular corrugated horns are more susceptible to these resonances than circular corrugated horns and the reasons are explained.



 

Prof. Jean-Charles Bolomey
Supelec, Electromagnetic Research Department
University Paris-Sud XI
France
bolomey@supelec.fr

 

Jean-Charles Bolomey is currently an Emeritus Professor at Paris-Sud University. He graduated from the Ecole Supérieure d’Electricité (Supelec) in 1963, received his Ph.D. degree from Paris-Sud University in 1971, and became a Professor at this University in 1976. His research has been conducted in the Electromagnetic Research Department of the Laboratoire des Signaux et Systèmes, a joint unit of Supelec and the National Center for Scientific Research (CNRS).

 

Since 1981, his research contributions have been devoted to Near-Field techniques in a broad sense, including antenna measurement, EMC testing as well as Industrial-Scientific-Medical (ISM) applications. These contributions have largely concerned measurement techniques and have been deliberately oriented toward innovative technology transfer and valorization. Jean-Charles Bolomey has more particularly promoted the modulated probe array technology, demonstrating its unrivaled potential for rapid Near-Field scanning. He has co-authored with Professor F.Gardiol a reference book on principles and applications of the Modulated Scattering Technique (MST). He is holder of numerous patents covering various MST-based probe array arrangements for microwave sensing and imaging systems. In 1986, under the impulse of the National Agency for Valorization (ANVAR) and of the CNRS, Professor Bolomey founded the Société d’Applications Technologiques de l’Imagerie Micro-Onde (SATIMO), which is now considered as a leading company in the field of antenna measurement. He has been also involved in industrial applications of microwave heating as a Chairman of the Microwave Group of Electricité de France (EDF) and was appointed as a consultant by the Délégation Générale de l’Armement (DGA) in the field of High Power Microwave (HPM) metrology. He has also actively contributed to several cooperative European Programs ranging from medical hyperthermia to industrial process tomography and has contributed to various prototype transfer and evaluation procedures in these areas. Recently, his research was related to RF dosimetry and rapid SAR measurements for wireless communication devices. Professor Bolomey his now continuing his research on load-modulated scattering antennas, and, more particularly, novel sensing applications of RFID technology. He is also contributing as a member of several Scientific Advisory Boards of European Institutions (Chalmers University, Queen Mary London University) and startup companies.

 

Jean-Charles Bolomey has received several awards, including the Blondel Medal of the Société des Electriciens et des Electroniciens (SEE) in 1976, the Général Ferrié Award of the French Academy of Sciences in 1984, and the Best Paper Award of the European Microwave Conference (EuMC) in 1983. In 1994, he has granted the Schlumberger Stitching Fund Award for his contribution to inverse scattering techniques in microwave imagery. In 2001, he has received the Distinguished Achievement Award of the Antenna Measurement Technique Association (AMTA) for his pioneering activity in the field of modulated probe arrays, and in 2007, elected as Edmond S. Gillespie Fellow for AMTA. He received the 2004 Medal of the French URSI Chapter. He has obtained the 2006 H.A. Wheeler Best Application Prize Paper Award of the IEEE AP-Society for his co-authored paper on “Spherical Near-Field Facility for Characterizing Random Emissions”. Professor Bolomey is Fellow of the Institution of Electrical and Electronic Engineers (IEEE) and received the Grade Emeritus of SEE in 1995.

 

Scattering by Load-Modulated Antennas: Background and Sensing Applications


While transmitting and receiving properties of antennas are fully formulated and well understood, scattering issues remain more mysterious, even if they have been extensively exploited for a while in the antenna engineer practice for shaping radiation patterns, adjusting input impedances, or for characterization purposes. This presentation is more specifically focused on modulated scattering-based systems, which have been successfully developed during the last decades. Operating an antenna in a scattering mode allows avoiding any RF front-end, resulting in very simple and compact passive or battery-assisted transponders. These advantages are now widely exploited in low-cost RFID tags, as well as in low-invasive MST (Modulated Scatterer Technique) probes for EM-field measurements.


This presentation consists of two major parts. The first one consists of a short tutorial review of the minimum engineering background required for a comprehensive approach to modulated scattering systems. Small antennas will be more particularly considered because low-invasiveness and high spatial resolution constitute significant advantages in many sensing applications. The power budget, a key issue for such systems, is derived from a very simple reciprocity-based formulation. The advantage of this analytical formulation is to apply, whatever the distance, for arbitrarily complex scenarios. In addition, the influence of various parameters can be clearly identified, paving the way for optimizing the antenna design in terms of global system performance. Examples of both active and passive scatterers illustrate the efficiency of this approach.

 

The second part is more speculative and aims to identify transfer opportunities between RFID’s and MST technologies for sensing applications. As compared to existing MST probes, passive RFID tags offer, at a glance, the indisputable advantage of being modulated from their own, without any wire or fiber. However, they may suffer autonomy/life time limitations and are constrained by standard regulations in terms of frequency range and power level. Furthermore, they exhibit specific technical difficulties, such as non-linearity of the IC chips loading the antenna. Various solutions to these drawbacks are addressed. Focusing on the case of systems involving arrays of modulated scatterers for its growing relevance in rapid imaging and wireless sensing (e.g. antenna measurement, industrial testing, medical diagnostic…), it is explained how the architecture of MST systems has conceptually changed during the last decades, primarily to face the critical sensitivity issue. Extrapolating such an evolution suggests promising solutions based on either RFID-derived or breakthrough technologies. To conclude, it is remembered that, while microwaves suffer no competition in the field of communications, they are loosing this comfortable privilege for Industrial Scientific Medical (ISM) applications where they must compete with many other efficient and already well-established modalities. In this competition, new modulated scattering technologies are reasonably expected contributing to valorize the specific advantages already recognized to RF- and microwave-based sensing modalities.



Near Field and Very-Near-Field Techniques: Current Status and Future Trends


The use of Near-Field (NF) techniques for antenna measurements is now well recognized in the antenna engineering practice. In the same time, Very-Near-Field (VNF) techniques are increasingly used for EMC applications. While such techniques suffered, during a long time, an apparent complexity resulting from the need of Near-to-Far Field transformation, recent advances in both software and equipment make them now fully accepted for their accuracy and flexibility. Indeed, Near-to-Far-Field transformations are now very efficiently achieved at moderate computational cost, even with regular PC’s. Furthermore, the major drawback of NF techniques, which consisted in the slowness of the measurement procedure, has been spectacularly overcome thanks to the use of probe arrays. Today, NF and VNF approaches appear as a very efficient way for obtaining, via computation, a maximum of information on intentional or non-intentional radiating system from a minimum number of measurements. Initially devoted to large antennas, NF techniques also constitute an attractive tool for rapid measurements on small antennas. More generally, as compared to direct measurement techniques involving long or compact ranges, they are much less space demanding and, consequently, they require smaller investments.

 

This presentation starts with briefly reviewing basic features of standard NF techniques based on a modal expansion of the radiated field. As an example, the test case of a base station antenna is considered. It is shown that, from a very limited number of NF data on a cylinder surface, it is possible, not only to calculate its radiation pattern in free-space, but also to check the compliance with reference levels or SAR basic restrictions in the close vicinity of the antenna, as well as to predict the field radiated, at any distance, in complex environments, thanks to appropriate codes. In a second time, inverse source algorithms are introduced. As compared to the modal expansion approach, these algorithms are relaxing some constraints on the number and distribution of sampling points, and those resulting from truncating the measurement surface. This last advantage is particularly interesting for VNF-based source modeling of unwanted radiation from electronic circuits or electrical components. However, they are more demanding in terms of computational effort, and suffer usual drawbacks of inverse problems. More prospectively, two other major aspects of NF and VNF techniques are considered. The first one is related to “phaseless” field or source reconstruction algorithms. Such algorithms are welcome when phase measurements are difficult (e.g. antennas in mm and sub-mm waves) or impossible (e.g. modulated signals of active antennas or spurious emissions for EMC applications). The second one deals with new generations of low-invasive sensors, which are currently developed. Their impact for VNF measurements is analyzed. To conclude, the extension of NF and VNF techniques to other applications such as medical diagnostic or industrial non-destructive testing is briefly presented.



Overview of Electromagnetic Scattering-Based Imaging Techniques


Making images consists in producing some footprints of a scene, allowing the human eye to view this scene. Intuitively, the footprint is supposed to show some kind of point-to-point correspondence between the scene and its image. Initially performed with natural light thanks to the human eye / brain combination, either alone or upgraded by means of optical instruments, the imaging procedures have been largely diversified during the last century. Such a diversification has been continuously stimulated by technological developments and led to consider new modalities to “see” objects escaping to human vision such as those buried in a medium opaque to the visible light. But penetrating opaque media usually requires operating at much larger than optical wavelengths, with the consequence that diffraction and scattering mechanisms, considered as second order perturbation in optical instruments, become first order effects decreasing image quality. For instance, the point-to-point correspondence between the observed object and its raw footprint is degraded or even may be apparently lost, requiring appropriate data processing. Many imaging systems dedicated to Industrial, Scientific, Security and Medical (IS2M) applications are based on electromagnetic waves, making them a convenient didactic support for a unified overview of scattering-based imaging techniques.

 

This presentation addresses two basic requirements for obtaining images of practical relevance. The first one is, evidently, that what one want to see is effectively visible. Such a visibility issue needs, beyond geometrical optics, entering into the details of scattering mechanisms. The second requirement is to be able to extract relevant images from measurements, by means of appropriate data acquisition and processing schemes. Setup geometry, number of measurement points, frequency band, measurement time, safety exposition standards, etc. constitute some examples of major experimental concerns, which, usually, must be optimized to comply with contradictory operational requirements. Processing techniques can be mainly categorized in linear and non-linear reconstructions. According to their complexity, which may vary in huge proportions, they can be implemented either in analogous or numerical ways, or by a combination of both.


Starting from well-known imaging modalities, such as optical 3D holography and X-Ray tomography, the imaging problem is considered under the more general inverse scattering point of view. After reviewing major setup geometries and related reconstruction algorithms, some guidelines to design an imaging system and optimize its performance are given. The selection of the operating frequency band is more particularly addressed, due to its decisive impact on image quality and system complexity. The case of microwaves will be more particularly developed from various viewpoints, including holography, tomography and Near-Field microscopy. Several examples of imaging systems dedicated to IS2M applications are presented to illustrate the current potential and limitations of such generalized imaging techniques. In conclusion, their expected evolution for the future is discussed.



Levent Gurel

Dept. of Electrical and Electronics Engineering
Director, Computational Electromagnetics Research Center (BiLCEM)
Bilkent University
TR-06800 Bilkent, Ankara Turkey
lgurel@ee.bilkent.edu.tr

 

Levent Gürel (S'87-M'92-SM'97-F'09) received the B.Sc. degree from the Middle East Technical University (METU), Ankara, Turkey, in 1986, and the M.S. and Ph.D. degrees from the University of Illinois at Urbana-Champaign (UIUC) in 1988 and 1991, respectively, all in electrical engineering.

He joined the Thomas J. Watson Research Center of the International Business Machines Corporation, Yorktown Heights, New York, in 1991, where he worked as a Research Staff Member on the electromagnetic compatibility (EMC) problems related to electronic packaging, on the use of microwave processes in the manufacturing and testing of electronic circuits, and on the development of fast solvers for interconnect modeling. Since 1994, he has been a faculty member in the Department of Electrical and Electronics Engineering of the Bilkent University, Ankara, where he is currently a Professor. He was a Visiting Associate Professor at the Center for Computational Electromagnetics (CCEM) of the UIUC for one semester in 1997. He returned to the UIUC as a Visiting Professor in 2003-2005, and as an Adjunct Professor after 2005. He founded the Computational Electromagnetics Research Center (BiLCEM) at Bilkent University in 2005, where he is serving as the Director.

 

Prof. Gürel's research interests include the development of fast algorithms for computational electromagnetics (CEM) and the application thereof to scattering and radiation problems involving large and complicated scatterers, antennas and radars, frequency-selective surfaces, high-speed electronic circuits, optical and imaging systems, nanostructures, and metamaterials. He is also interested in the theoretical and computational aspects of electromagnetic compatibility and interference analyses. Ground penetrating radars and other subsurface scattering applications are also among his research interests. Since 2006, his research group has been breaking several world records by solving extremely large integral-equation problems, most recently the largest involving as many as 540 million unknowns.

 

Among the recognitions of Prof. Gürel's accomplishments, the two prestigious awards from the Turkish Academy of Sciences (TUBA) in 2002 and the Scientific and Technical Research Council of Turkey (TUBITAK) in 2003 are the most notable.

 

He is a member of the USNC of the International Union of Radio Science (URSI) and the Chairman of Commission E (Electromagnetic Noise and Interference) of URSI Turkey National Committee. He served as a member of the General Assembly of the European Microwave Association (EuMA) during 2006-2008.

 

He is currently serving as an associate editor for Radio Science, IEEE Antennas and Wireless Propagation Letters, Journal of Electromagnetic Waves and Applications (JEMWA), and Progress in Electromagnetics Research (PIER).

 

Prof. Gürel served as the Chairman of the AP/MTT/ED/EMC Chapter of the IEEE Turkey Section in 2000-2003. He founded the IEEE EMC Chapter in Turkey in 2000. He served as the Cochairman of the 2003 IEEE International Symposium on Electromagnetic Compatibility. He is the organizer and General Chair of the CEM’07 and CEM’09 Computational Electromagnetics International Workshops held in 2007 and 2009, technically sponsored by IEEE AP-S.

 

Hierarchical Parallelization of the Multilevel Fast Multipole Algorithm (MLFMA)


It is possible to solve electromagnetics problems several orders of magnitude faster by using MLFMA. Without exaggeration, this means accelerating the solutions by thousands or even millions of times, compared to the Gaussian elimination. However, it is quite difficult to parallelize MLFMA. This is because of the already-too-complicated structure of the MLFMA solver. Recently, we have developed a hierarchical parallelization scheme for MLFMA. This novel parallelization scheme is both efficient and effective. This way, we have been able to parallelize MLFMA over hundreds of processors. By using distributed-memory architectures, this accomplishment translates into an ability to use more memory and to solve much larger problems than it was possible before. Unlike previous parallelization techniques, with the novel hierarchical partitioning strategy, the tree structure of MLFMA is distributed among processors by partitioning both clusters and samples of fields at each level. Due to the improved load-balancing, the hierarchical strategy offers a higher parallelization efficiency than previous approaches, especially when the number of processors is large. We demonstrate the improved efficiency on scattering problems discretized with millions of unknowns. We present the effectiveness of our algorithm by solving very large scattering problems.

 

Solution of World’s Largest Integral-Equation Problems


Accurate simulations of real-life electromagnetics problems with integral equations require the solution of dense matrix equations involving millions of unknowns. Solutions of these extremely large problems cannot be achieved easily, even when using the most powerful computers with state-of-the-art technology. However, with MLFMA and parallel MLFMA, we have been able to obtain full-wave solutions of scattering problems discretized with hundreds of millions of unknowns. Some of the complicated real-life problems (such as, scattering from a realistic aircraft) involve geometries that are larger than 1000 wavelengths. Accurate solutions of such problems can be used as reference data for high-frequency techniques. Solutions of extremely large canonical benchmark problems involving sphere and NASA Almond geometries will be presented, in addition to the solution of complicated objects, such as metamaterial problems, red blood cells, and dielectric photonic crystals. For example, by solving the world’s largest and most complicated metamaterial problems (without resorting to homogenization), we demonstrate how the transmission properties of metamaterial walls can be enhanced with randomly-oriented unit cells. Also, we present a comparative study of scattering from healthy red blood cells (RBCs) and diseased RBCs with deformed shapes, leading to a method of diagnosis of blood diseases based on scattering statistics of RBCs. We will present solutions of extremely large problems involving more than 500 million unknowns.


Novel and Effective Preconditioners for Iterative Solvers


Solutions of extremely large matrix equations require iterative solvers. MLFMA accelerates the matrix-vector multiplications performed with every iteration. Despite the acceleration provided by MLFMA, the number of iterations should also be kept at a minimum, especially if the dimension of the matrix is in the order of millions. This is exactly where the preconditioners are needed. We have developed several novel preconditioners that can be used to accelerate the solution of various problems formulated with different types of integral equations. For example, it is well known that the electric-field integral equation (EFIE) is worse conditioned than the magnetic-field integral equation (MFIE) for conductor problems. Therefore, the preconditioners that we develop for EFIE are crucial for the solution of extremely large EFIE problems. For dielectric problems, we formulate several different types of integral equations to investigate which ones have better conditioning properties. Furthermore, we develop effective preconditioners specifically for dielectric problems. In this talk, we will review three classes of preconditioners:

 

1. Sparse near-field preconditioners
2. Approximate full-matrix preconditioners
3. Schur complement preconditioning for dielectric problems

 

We will present our efforts to devise effective preconditioners for MLFMA solutions of difficult electromagnetics problems involving both conductors and dielectrics, such as the block-diagonal preconditioner (BDP), incomplete LU (ILU) preconditioners, sparse approximate inverse (SAI) preconditioners, iterative near-field (INF) preconditioner, approximate MLFMA (AMLFMA) preconditioner, the approximate Schur preconditioner (ASP), and the iterative Schur preconditioner (ISP).



Prof. Per-Simon Kildal
Antenna Group
Department of Signals and Systems
41296 Gothenburg
Sweden
per-simon.kildal@chalmers.se

 

Per-Simon Kildal (M’82-SM’84-F’95) has M.S.E.E., Ph.D., and Doc¬tor Technicae degrees from the Norwegian Institute of Technology (NTH) in Trondheim. He was with SINTEF research institute in Trondheim from 1979 till 1989, and since then he has been a Professor at Chalmers Uni¬versity of Technology, Gothenburg, Sweden, where he has educated 17 persons to a PhD in antennas.


Kildal has done several services to the IEEE Antennas and Propagation Society: elected member of the administration committee 1995-97, distinguished lecturer 1991-94, associate editor of the transactions 1995-98, and associate editor of a special issue in the transactions 2005. He has authored or coauthored more than 100 journal articles or letters in IEEE or IET journal, concerning antenna theory, analysis, design and measurement. He gives short courses and organizes special sessions at conferences, and he has given invited lectures in plenary sessions at several conferences. His textbook Founda¬tions of Antennas - A Unified Approach has been well received. SINTEF awarded his work in 1984. He has received two best paper awards in IEEE Transaction on Antennas and Propagation. He holds several granted patents and patents pending.


Kildal has done the electrical design of two very large antennas, including development of the numerical methods and software: the 40m x 120m cylindrical parabolic reflector antenna of the European Incoherent Scatter Scientific Association (EISCAT), and the Gregorian dual-reflector feed of the 300m diameter radio telescope in Arecibo, the latter on a contract for Cornell University. He has invented several feeds for reflector antennas, such as the dipole-disk feed used for 10 years in the commercial satcom ship terminal of the Norwegian company NERA, the hat feed used for 10 years in commercial radio links, and the decade bandwidth log-periodic Eleven feed developed for use in radio telescopes for VLBI2010 and Square Kilometer Array (SKA).


Kildal and his co-workers have pioneered the reverberation chamber to an accurate tool for Over-The-Air (OTA) testing of small antennas and wireless devices, being commercialized in the company Bluetest AB (www.bluetest.se). Bluetest was founded in 2000, and experiences now a rapid growth in the market.


Kildal introduced the concept of soft and hard surfaces in 1988, representing a generalization of the corrugated surface, and having similarities with the later electromagnetic bandgap surface. The soft and hard surfaces are today considered as metamaterials. On this background he invented in 2008 a new quasi-TEM so-called gap waveguide that appears in the air gap between two parallel conducting plates. The gap waveguide has been demonstrated to have decade bandwidth, low loss, and application for packaging of electronic high-frequency circuits. It is expected to find application up to THz.

 

Gap Waveguides and Antennas up to Terahertz


The gap waveguide is a new quasi-TEM transmission line appearing in the air gap between two parallel metal plates, one of which is provided with a texture or a substrate with metal traces and patches. The waves follows strips, ridges or grooves in the texture, and are prohibited from propagating in other directions within a stopband realized by periodicities in the texture, thereby avoiding the need for conducting contact between the two metal plates. Such conducting contact is needed in normal cylindrical waveguides, and is known to be difficult and expensive to realize, in particular above 30 GHz. The waveguide has been demonstrated to have low losses and octave bandwidth. It can be potentially be applied to realize high-frequency circuits up to THz, and has demonstrated that it also can be used for packaging of passive and active circuits realized by other transmission line technologies.


The lecture will explain how the gap waveguides have evolved from research on artificial surfaces, such as the soft and hard surfaces defined in 1988, and the later high-impedance surfaces (artificial magnetic conductors) and electromagnetic bandgap (EBG) surfaces. The ideal counterparts of such surfaces can be called canonical surfaces, and Kildal states the need for the boundary conditions of the canonical surfaces to be built into commercial electromagnetics software to enable fast initial feasibility studies and designs.


The lecture will then give the basic theory of the gap waveguides and explain how they work, describe how to design the stopband of normal parallel-plate modes using different periodic metal elements, such as pins (nails), patches with via holes (mushrooms), and helices (springs), introduce the three different realizations of it referred to as ridge, strip and groove gap waveguides, and show examples of antennas and components such as OMT, couplers and filters realized in this technology. Examples of packaging applications will also be shown, using a lid of springs at low frequencies and a lid of nails at high frequencies, as well as a systematic advantageous approach to packaging referred to as PMC packaging, in which the circuit design is done inside a PEC/PMC package, and thereafter the PMC is realized.

 

OTA-MIMO Measurements of Wireless Stations in Reverberation Chamber

 

Antenna measurements are normally done in anechoic chambers emulating free space, because free space is a good reference environment for traditional antenna locations on roof-tops and masts with Line-Of-Sight (LOS) to the opposite side of the communication link or target. However, modern small antennas on wireless stations are not located on mast and rooftops, and they are exposed to multipath often without LOS, and a resulting fading. Therefore, a new reference environment is needed for Over-The-Air (OTA) tests, such as the isotropic multipath environment emulated by a reverberation chamber. Also, modern wireless stations have or will be provided with multi-port small antennas combating the negative effects of fading by antenna diversity and MIMO (Multiple Input Multiple Output) technology, and then it is also needed to emulate a fading-type reference environment to test these functions, such as that emulated by reverberation chambers.


The rich isotropic reference environment has a uniform Angle-of-Arrival (AoA) distribution, for which the average received power is proportional to antenna efficiency and total radiated power and independent of the orientation of the antenna and wireless station. A wireless station will also in average experience a rich isotropic environment when it is moved between different real-life environments, and in particular if it has an arbitrary orientation with respect to the vertical when it is used. Therefore, the rich isotropic multipath is believed to be a good new reference environment for OTA tests of wireless stations for use in multipath.


The reverberation chamber has during the last 10 years been developed into a fast, accurate and cost-effective instrument for emulating rich isotropic multipath and thereby characterizing small antennas and wireless stations. The lecture will explain how the chamber works, and give formulas for the average transfer function as well as the uncertainty by which we can measure efficiency, diversity gain, maximum available MIMO capacity, total radiated power and receiver sensitivity. The latter can be obtained both as total isotropic sensitivity (TIS) and average fading sensitivity (AFS), the latter measured during continuous fading.


The last part of the lecture will be devoted to through-put measurements of complete systems with MIMO capability, such as for WLAN, LTE and WiMAX. The lecture will also explain how the time and frequency domain characteristics of the chamber (Doppler spread, time delay spread, coherence bandwidth) can be determined, and controlled by loading the chamber with absorbing objects.

 

Low Noise Decade-Bandwidth Eleven feed for Future Radio Telescopes

 

The Eleven antenna is a log-periodic dual-polarized dual-folded-dipole antenna with constant beamwidth and phase center over a decade bandwidth. The antenna is mainly intended as a feed for Square Kilometer Arrays (SKA) and geodetic VLBI2010 radio telescopes, but several other applications are possible e.g. in anechoic far-field or compact ranges, and for EMC. The Eleven antenna can easily be reconfigured for use with 2-ports, 4-ports or 8-ports which makes it interesting for use in connection with MIMO communication systems or as a multi-port wideband reference antenna for testing/validation of these.


The lecture will first give an introduction to common feeds for reflector antennas and how their radiation fields can be characterized in terms of the feed efficiency and its subefficiencies accounting for spillover, illumination taper, phase errors, and polarization loss. This characterization is sufficient for normal feeds, but it will be argued that for antennas with octave or more bandwidth an additional so-called “BOR1” subefficiency is needed in order to characterize how clean the radiation pattern is with respect to higher order azimuth variations in the far-field function.
The lecture will describe how the Eleven antenna has been numerically optimized and designed to achieve high feed efficiency over a decade bandwidth, without performance notches. The description includes co-design and integration with low-noise amplifiers (LNA), and cryogenic mechanical design allowing for cooling down to 20 K together with the LNAs. A model for the overall achieved system noise temperature will be presented, agreeing well with measured performance.


Finally, the lecture will give results for measured and computed correlation and diversity gain as a function of frequency when the multi-port Eleven antenna is used in a MIMO system.


 

Prof. Jin-Fa Lee
ElectroScience Laboratory
ECE Department
The Ohio State University
1320 Kinnear Rd.
Columbus, OH 43212
lee.1863@osu.edu

 

Jin-Fa Lee received the B.S. degree from National Taiwan University, in 1982 and the M.S. and Ph.D. degrees from Carnegie-Mellon University in 1986 and 1989, respectively, all in electrical engineering. From 1988 to 1990, he was with ANSOFT (later acquired by ANSYS) Corp., where he developed several CAD/CAE finite element programs for modeling three-dimensional microwave and millimeter-wave circuits. From 1990 to 1991, he was a post-doctoral fellow at the University of Illinois at Urbana-Champaign. From 1991 to 2000, he was with Department of Electrical and Computer Engineering, Worcester Polytechnic Institute. He joined the Ohio State University at 2001 where he is currently a Professor in the Dept. of Electrical and Computer Engineering. Prof. Lee is an IEEE fellow and is currently serving as an associate editor for IEEE Trans. Antenna Propagation. Also, he is a member of the Board of Directors for Applied Computational Electromagnetic Society (ACES).

 

Prof. Lee’s main research interests include electromagnetic field theories, antennas, numerical methods and their applications to computational electromagnetics, analyses of numerical methods, fast finite element methods, fast integral equation methods, hybrid methods, domain decomposition methods, and multi-physics simulations and modeling.

 

CEM Algorithms for EMC/EMI Modeling: Electrically Large (Antenna Placements on Platforms) and Small (SI in ICs and Packaging) Problems


Modern antenna engineering often involves the use of metamaterials, complex feed structures, and conformally mounting on large composite platforms. However, such antenna systems do impose significant challenges for numerical simulations. Not only do they usually in need of large-scale electromagnetic field computations, but also they tend to have many very small features in the presence of electrically large structures. Such multi-scale electromagnetic problems tax heavily on numerical methods (finite elements, finite difference, integral equation methods etc.) in terms of desired accuracy and stability of mathematical formulations.

Another important electromagnetic application is the study of signal integrity in ICs. Recent advances in VLSI interconnect and packaging technologies, such as the increasing number of metal layers and the 3D integration, have paved the way for higher functionality and superior performances. During the reduction of the size, power, and cost in today’s advanced IC interconnects and packaging, the signal integrity (SI) has become more crucial for system designers. The previous common practice adopted by industries, such as using only static parasitic RC or RLC equivalent networks for physical designs, are gradually abandoned. It has come to use full-wave computational electromagnetic (CEM) methods for the ultimate accuracy check.

 

In this lecture, I will present our on-going efforts in combating the multi-scale electromagnetic problems, both electrically large (antenna placements on platforms) and electrically small but complex (SI in ICs) through the use of non-conventional PDE methods that are non-conformal. The non-conformal numerical methods relax the constraint of needing conformal meshes throughout the entire problem domain. Consequently, the entire system can be broken into many sub-problems, each has its own characteristics length and will be meshed independently from others. Particularly, our discussions will include the following topics:

 

  • Integral Equation Domain Decomposition Method (IE-DDM): A very significant breakthrough that has been accomplished is the IE-DDM formulation. For example, we show an electromagnetic plane wave scattering from a mock-up fighter –jet with thin coatings at the X- and Ku-bands by dividing the platform into many closed objects, and noting that they will be touching each other through common interfaces.
  • Non-Conformal DDM with Higher Order Transmission Conditions and Corner Edge Penalty: By introducing two second-order transverse derivatives, one for TE and one for TM, the derived 2nd order TC provides convergence for both the propagating and evanescent modes. Moreover, on the corner edges sharing by more than two domains, an additional corner edge penalty term needs to be added in the variational formulation. Consequently, the robustness of the non-conformal DDMs is now firmly established theoretically and numerically.
  • Multi-region/Multi-Solver DDM with Touching Regions: Many multi-scale physical problems are very difficult, if not impossible, to solve using just one of the existing CEM techniaues. We have been pursuing a multi-region multi-solver domain decomposition method (MS-DDM) to effectively tackle such problems. Various CEM solvers are now integrated into a MS-DDM code and collectively, it emerges as the only alternative for solving many real-life applications that were thought un-solvable before.
  • Discontinuous Galerkin Time Domain (DGTD) Method with Hierarchical MPI-CUDA GPU Implementation: We shall also discuss in some details, our on-going efforts in the time domain simulation, the DGTD algorithm. Particularly, the use of graphical process unit (GPU) in speeding up the DGTD computations.

 

Science and Applications of CEMs and Multi-Physics Computations


Computational Electromagnetics (CEM) techniques, such as FDTD, BEM (or Method of Moments), FEM, are playing increasingly important roles in many electromagnetic applications. In this lecture, I shall first describe the fundamental principles behind the popular CEM methods, and elucidate their corresponding strengths and weaknesses.

 

The second part of the lecture focuses on how to combine a suite of CEM techniques and couplings of multi-physics modelling to solve challenging real-life engineering applications. Particularly, the following three main topics will be emphasized:

 

  • Full wave solutions of EM radiations and scatterings in the vicinity of large composite platforms (with various thin coatings and exotic metamaterials). The multi-scale nature and fine geometrical features of this application tax significantly on engineering ingenuity. As a consequence, a plethora of novel CEM techniques, including multi-solver DDM, DDM for general integral equations for both PEC and lossy dielectric materials, PDE methods using polyhedral elements instead of conventional brick and tetrahedral elements, and the material homogenization, have been developed to mitigate these technical challenges directly.
  • Co-design suite for modelling antenna systems (with front end electronics) and full IC packages taking into account both EM and thermal effects. In many real-life antenna systems, the temperature distributions in the environment as well as within the antennas affect greatly the overall system performance. Moreover, the signal and power integrity analyses for full IC packages usually require considerations of conductor losses, which are in general functions of the temperature. The multi-physics coupling, both in the frequency and time domains, between EM and thermal effects are the main concern in this topic.
  • Large land vehicles on lossy rough surfaces, microwave imaging, and modelling 3D rough surface and random multi-layer media for applications in LCDs, organic LEDs. New simulation and modelling techniques are pursued diligently to address this application area, and preliminary results are promising.



 

Prof. Joshua Le-Wei Li
QRJH Chair (National) Professor, School of Electronic Engineering
Director, Institute of Electromagnetics
University of Electronic Science and Technology of China
2006 Xi-Yuan Avenue, Western High-Tech District
Chengdu, China 611731
lwli@ieee.org

 

Joshua Le-Wei Li (SM'96-F'05) received his Ph.D. degree in Electrical Engineering from Monash University, Melbourne, Australia, in 1992. He was, as a Research Fellow, with Department of Electrical & Computer Systems Engineering at Monash University, sponsored in 1992 by Department of Physics at La Trobe University, both in Melbourne, Australia. Between 1992-2010, he was with the Department of Electrical & Computer Engineering at the National University of Singapore where he was a tenured Full Professor and the Director of NUS Centre for Microwave and Radio Frequency. In 1999-2004, he was seconded with High Performance Computations on Engineered Systems (HPCES) Programme of Singapore-MIT Alliance (SMA) as a SMA Faculty Fellow. In May-July 2002, he was a Visiting Scientist in the Research Laboratory of Electronics at Massachusetts Institute of Technology (MIT), Cambridge, USA; in October 2007, an Invited Professor with University of Paris VI, France; and in January and June 2008, an Invited Visiting Professor with Institute for Transmission, Waves and Photonics at Swiss Federal Institute of Technology, Lausanne (EPFL) in Switzerland. Currently, he is with School of Electronic Engineering at University of Electronic Science and Technology of China, Chengdu, China where he is a QRJH Chair (or National) Professor and a founding Director of Institute of Electromagnetics. His current research interests include electromagnetic theory (e.g., dyadic Green's functions), computational electromagnetics (e.g., pre-corrected fast Fourier transform - P-FFT method and adaptive integral method -AIM), radio wave propagation and scattering in various media (e.g., chiral media, anisotropic media, bi-anisotropic media and metamaterials), microwave propagation and scattering in tropical environment, and analysis and design of various antennas (e.g., loop and wire antennas and microstrip antennas). In these areas, he has (co-)authored 2 books (namely, Spheroidal Wave Functions in Electromagnetic Theory (New York: Wiley, 2001); Device Modeling in CMOS Integrated Circuits: Interconnects, Inductors and Transformers (London: Lambert Academic Publishing, 2010), 48 book chapters, over 310 international refereed journal papers (of which more than half were published in IEEE Transactions and Letters, and the remaining in Optics Express, Physical Review E or B, Radio Science, IEE Proceedings, and JEWA etc), 48 regional refereed journal papers, and over 350 international conference papers. He has graduated about 70 Master-degree and PhD-degree students, and mentored over 20 post-doctoral fellows and research scientists.

 

Prof. Li was a recipient of a few awards including 2 best paper awards from the Chinese Institute of Communications and the Chinese Institute of Electronics, the 1996 National Award of Science and Technology of China, the 2003 IEEE AP-S Best Chapter Award when he was the IEEE Singapore MTT/AP Joint Chapter Chairman, and the 2004 University Excellent Teacher Award of National University of Singapore. He has been a Fellow of IEEE since 2005 and a Fellow of The Electromagnetics Academy since 2007 (selected member since 1998) and was IEICE Singapore Section Chairman between 2002-2007. As a regular reviewer of many archival journals, he is currently an Associate Editor of Radio Science and International Journal of Antennas and Propagation; an Editorial Board Member of Journal of Electromagnetic Waves and Applications (JEWA), the book series Progress In Electromagnetics Research (PIER) by EMW Publishing, International Journal of Microwave and Optical Technology, and Electromagnetics journal; and an Overseas Editorial Board Member of Chinese Journal of Radio Science and Frontiers of Electrical and Electronic Engineering in China (for selected papers from Chinese Universities by Springer). He was also a Guest Editor of a Special Section on ISAP 2006 of IEICE Transactions on Communications, Japan. He also serves as a member of various International Advisory Committee and/or Technical Program Committee of many international conferences or workshops, in addition to serving as a General Chairman of ISAP2006 & IWM2009 and TPC Chairman of PIERS2003, iWAT2006 and APMC2009.

 

Wideband and Low-Loss Metamaterials for Microwave and RF: Fast Algorithm and Applications


Over the past several years, the metamaterials research has been intensively conducted for the microwave and radio frequency (RF) applications. However, difficulties were faced and are still being faced right now in the developments of (1) efficient solvers and/or tools for metamaterial designs; and (2) design and fabrications of metamaterials of low loss and broad frequency bandwidth. Although these are not key issues in optical region, they are in fact the major issues of the metamaterial research in microwave and RF region. This talk is split into two major parts: (1) the first is to look into the EM wave properties in metamaterials and to develop efficient solvers for their designs; and (2) the second is to try to design the metamaterials for antenna applications.

 

For the efficient algorithms developed, the integral equation solvers accelerated using the adaptive integral (equation) method (AIM) and also the pre-corrected fast Fourier transform (pFFT) technique were developed and various examples in the designs will be demonstrated. In the second case, a single antenna designed using the metamaterial properties is considered, designed, fabricated, and measured. It is shown that the new design of the metamaterial antenna has a low loss (or high gain) and a broad bandwidth and this was never achieved using the conventional technique. The development of the metamaterial antennas was further extended to an array antenna and some interesting and promising results will be provided. A comprehensive review on the to-date progress on the metamaterials will be also provided.


Fast Solvers Based on Hybrid FFT-Integral Equations for Design & Analysis of Large Scaled Systems


In computational electromagnetics, three common methods are mostly frequently applied in the community for solving various practical applications, namely, (a) finite-difference time-domain (FDTD) method, (b) finite element method (FEM), and (c) integral equation method (IEM) including the method of moments (MoM) and the boundary element method (BEM). For very large scaled problems, the fast solvers are needed to accelerate the solution process. Associated with the large scaled problems, the FEM and IEM are very efficient to handle. To accelerate the IEM or MoM solution procedure, the fast multipole method (or its high level version, multi-level fast multipole algorithm (MLFMA)) and the fast-Fourier-transform based methods are very popular to use. In this talk, 3 fast algorithms developed based on integral equations and fast Fourier transform will be presented, namely, Conjugate Gradient Fast Fourier Transform (CG-FFT) Technique, Adaptive Integral (Equation) Method (AIM), and Precorrected Fast Fourier Transform (pFFT) method. These 3 methods have found extensive applications in the printed circuit designs, antenna analysis and design, radar cross section control, etc. Together with the latest growth of the computer facilities and advances of computing power, these techniques developed have made many past unsolved large scaled electrical engineering problems to be solvable. Some practical examples were solved using these techniques and results obtained using them will be demonstrated so as to show the accuracy, efficiency, and applicability of these techniques developed only the recent decade. Comparative studies using above different techniques are also presented to show the efficiency and accuracy, with emphasis given to the respective advantages and disadvantages of the above different groups of methods.


 

Prof. Sembiam R. Rengarajan
Department of Electrical and Computer Engineering
California State University
Northridge, CA 91330
srengarajan@csun.edu

 

Sembiam R. Rengarajan received the Ph.D. degree in Electrical Engineering from the University of New Brunswick, Canada in 1980. Since then he has been with the department of Electrical and Computer Engineering, California State University, Northridge (CSUN), CA, presently serving as a Professor. His experience includes periods at Bharat Electronics Ltd., India, Jet Propulsion Laboratory (JPL), Chalmers University of Technology, Sweden, US Air Force Research Laboratory, and Naval Research Lab., Washington, D.C. He has held visiting professorships at UCLA, Universidade de Santiago de Compostela, Spain, the University of Pretoria, South Africa, and the Technical University of Denmark. He has served as a consultant to Hughes Aircraft Company, Rantec, Saab Ericsson Space, Sweden, Lockheed Martin, United Nations Development Program in India, and URS Alaska. His research interests include analytical and numerical techniques in electromagnetics with applications to antennas, scattering, and passive microwave components.


Dr. Rengarajan has authored/co-authored more than 200 journal articles and conference papers. He is a Fellow of IEEE (1994), and a Fellow of the Electromagnetics Academy. He served as the Chair of the LA Chapter of IEEE Antennas and Propagation Society (1983-84), Chair of the San Fernando Valley Section of IEEE (1995), and as an Associate Editor of the IEEE Transactions on Antennas and Propagation (2000-2003). He was the Chair of the Education Committee of the IEEE Antennas and Propagation Society and was an Associate Editor of the IEEE Antennas and Propagation Magazine. He received the Preeminent Scholarly Publication Award from CSUN in 2005, CSUN Research Fellow Award in 2010, and a Distinguished Engineering Educator of the Year Award from the Engineers' Council of California in 1995. Dr. Rengarajan received more than a dozen awards from the National Aeronautics and Space Administration (NASA) for his innovative research and technical contributions to the Deep Space Network Ground Systems Antennas and to the Spacecraft Antenna Research Group of JPL. In 2005 he was appointed as an Adjunct Professor at the Electromagnetics Academy of Zhejiang University in China. He was the guest editor of a special issue of Electromagnetics on slot arrays. He has served in the technical program committee of several symposia and serves as a reviewer to many periodicals. Dr. Rengarajan is presently the Vice Chair and Chair-Elect of the Commission on Waves and Fields of the United States National Committee of the International Union of Radio Science (USNC/URSI) during the 2009-2011 triennium.

 

Design, Analysis, and Applications of Waveguide-Fed Slot Arrays


Waveguide-fed slot arrays find applications in numerous radar, remote sensing, and communication systems because of desirable features such as low loss integrated feed, and low volume. Accurate electromagnetic analysis and design tools have made it possible to produce such antennas in ‘one pass’ without any hardware iterations and still meet the stringent specifications commonly encountered. Because of the all metal construction, slot arrays are ideally suited to withstand severe radiation environment encountered in spacecraft applications.

 

This presentation will start with Elliott’s procedure for designing waveguide fed linear and planar slot arrays. The required input data such as the scattering characteristics of isolated radiating and coupling elements may be obtained, based on techniques such as the method-of-moments solution of the pertinent integral equations (M0M), or finite element techniques, e.g., using the commercial code HFSS, while the excitation coefficients are determined from a pattern synthesis technique. Stegen-type normalization or an interpolation technique will be used with the computed slot data. External mutual coupling computation in the form of ‘element by element’ model is ideal for small to medium arrays while Floquet series of the infinite array model is suited for large arrays. Different types of feeds and sub-array architectures will be reviewed. Efficient implementation of Elliott’s algorithm with choices for the values of radiating slot admittances and coupling slot impedances will be presented. Analysis techniques such as MoM and HFSS are employed to validate and assess the performance of the arrays. Enhancements to Elliott’s technique that account for higher order mode coupling will be discussed. The use of full wave method-of-moments technique in improving the design procedure will be illustrated. Some recent examples of practical slot arrays antennas for different applications will be presented.

 

The talk will be tailored to the audience by emphasizing the topics of interest.


 

Prof. Tapan K. Sarkar
Department of Electrical Engineering and Computer Science
Syracuse University
323 Link Hall
Syracuse, NY 13244-1240
tksarkar@syr.edu

 

Tapan K. Sarkar received the B.Tech. degree from the Indian Institute of Technology, Kharagpur, in 1969, the M.Sc.E. degree from the University of New Brunswick, Fredericton, NB, Canada, in 1971, and the M.S. and Ph.D. degrees from Syracuse University, Syracuse, NY, in 1975. From 1975 to 1976, he was with the TACO Division of the General Instruments Corporation. He was with the Rochester Institute of Technology, Rochester, NY, from 1976 to 1985. He was a Research Fellow at the Gordon McKay Laboratory, Harvard University, Cambridge, MA, from 1977 to 1978. He is now a Professor in the Department of Electrical and Computer Engineering, Syracuse University. His current research interests deal with numerical solutions of operator equations arising in electromagnetics and signal processing with application to system design. He obtained one of the “best solution” awards in May 1977 at the Rome Air Development Center Spectral Estimation Workshop. He received the Best Paper Award of the IEEE Transactions on Electromagnetic Compatibility in 1979 and in the 1997 National Radar Conference. He has authored or coauthored more than 300 journal articles and numerous conference papers and 32 chapters in books and fifteen books, including his most recent ones, Iterative and Self Adaptive Finite-Elements in Electromagnetic Modeling (Boston, MA: Artech House, 1998), Wavelet Applications in Electromagnetics and Signal Processing (Boston, MA: Artech House, 2002), Smart Antennas (IEEE Press and John Wiley & Sons, 2003), History of Wireless (IEEE Press and John Wiley & Sons, 2005), Physics of Multiantenna Systems and Broadband Adaptive Processing (John Wiley & Sons, 2007), Parallel Solution of Integral Equation-Based EM Problems in the Frequency Domain (IEEE Press and John Wiley & Sons, 2009), and Time and Frequency Domain Solutions of EM Problems Using Integral Equations and a Hybrid Methodology (IEEE Press and John Wiley & Sons, 2010).

 

Dr. Sarkar is a Registered Professional Engineer in the State of New York. He received the College of Engineering Research Award in 1996 and the Chancellor’s Citation for Excellence in Research in 1998 at Syracuse University. He was an Associate Editor for feature articles of the IEEE Antennas and Propagation Society Newsletter (1986-1988), Associate Editor for the IEEE Transactions on Electromagnetic Compatibility (1986-1989), Chairman of the Inter-commission Working Group of International URSI on Time Domain Metrology (1990–1996), distinguished lecturer for the Antennas and Propagation Society from (2000-2003), Member of Antennas and Propagation Society ADCOM (2004-2007), on the board of directors of ACES (2000-2006), vice president of the Applied Computational Electromagnetics Society (ACES), a member of the IEEE Electromagnetics Award board (2004-2007), and an associate editor for the IEEE Transactions on Antennas and Propagation (2004-2010). He is currently on the editorial board of Digital Signal Processing – A Review Journal, Journal of Electromagnetic Waves and Applications and Microwave and Optical Technology Letters. He is the chair of the International Conference Technical Committee of IEEE Microwave Theory and Techniques Society # 1 on Field Theory and Guided Waves.

 

He received Docteur Honoris Causa both from Universite Blaise Pascal, Clermont Ferrand, France in 1998 and from Politechnic University of Madrid, Madrid, Spain in 2004. He received the medal of the friend of the city of Clermont Ferrand, France, in 2000.

 

Physics of Multiantenna Systems and their Impacts on Wireless Systems


The objective of this presentation is to present a scientific methodology that can be used to analyze the physics of multiantenna systems. Multiantenna systems are becoming exceedingly popular because they promise a different dimension, namely spatial diversity, than what was available to the communication systems engineers: The use of multiple transmit and receive antennas provides a means to perform spatial diversity, at least from a conceptual standpoint. In this way, one could increase the capacities of existing systems that already exploit time and frequency diversity. In such a scenario it could be said that the deployment of multiantenna systems is equivalent to using an overmoded waveguide, where information is simultaneously transmitted via not only the dominant mode but also through all the higher-order modes. We look into this interesting possibility and study why communication engineers advocate the use of such systems, whereas electromagnetic and microwave engineers have avoided such propagation mechanisms in their systems. Most importantly, we study the physical principles of multiantenna systems through Maxwell’s equations and utilize them to perform various numerical simulations to observe how a typical system will behave in practice. There is an important feature that is singular in electrical engineering and that many times is not treated properly in system applications: namely, superposition of power does not hold.

 

Consider two interacting plane waves with power densities of 100 and 1 W/m2. Even though one of the waves has only 1% of the power density of the other wave, if the two waves interfere constructively or destructively, the resulting variation in the received power density is neither 101 nor 99 W/m2, but rather is 121 or 81 W/m2, respectively. [constructive: 121= destructive: 81= ]. Hence, there is a 40% variation. Using power additively leads to a significant error in the received power density. The key point here is that the fields or amplitudes can be added in the electrical engineering context and NOT the powers. This simple example based on Maxwellian physics clearly illustrates that the materials available in standard text books on Wireless Communication which claims that “an M-element array, in general, can achieve a signal-to-noise ratio improvement of 10log10(M) in the presence of Additive White Gaussian Noise with no interference or multipath over that of a single element” has to be taken with a big grain of salt. Hence, we need to be careful when comparing the performance of different systems in making valued judgments. In addition, appropriate metrics which is valid from a scientific standpoint should be selected to make this comparison. Examples will be presented to illustrate how this important principle impact certain conventional way of thinking in wireless communication.

 

Also, we examine the phenomenon of height-gain in wireless cellular communication, and illustrate that under the current operating scenarios where the base station antennas are deployed over a tall tower, the field strength actually decreases with the height of the antenna over a realistic ground and there is no height gain in the near field. Therefore, to obtain a scientifically meaningful operational environment the vertically polarized base station antennas should be deployed closer to the ground. Also, when deploying antennas over tall towers it may be more advantageous to use horizontally polarized antennas than vertically polarized for communication in cellular environments. Numerical examples are presented to illustrate these cases.

 

We next look at the concept of channel capacity and observe the various definitions of it that exist in the literature. The concept of channel capacity is intimately connected with the concept of entropy, and hence related to physics. We present two forms of the channel capacity, the usual Shannon capacity which is based on power; and the seldom used definition of Hartley which uses values of the voltage. These two definitions of capacities are shown to yield numerically very similar values if one is dealing with conjugately matched transmit-receive antenna systems. However, from an engineering standpoint, the voltage-based form of the channel capacity is more useful as it is related to the sensitivity of the receiver to an incoming electromagnetic wave. Furthermore, we illustrate through numerical simulations how to apply the channel capacity formulas in an electromagnetically proper way. To perform the calculations correctly in order to compare different scenarios, in all simulations the input power fed to the antennas needs to remain constant. Also conclusions should not be made using the principles of superposition of power. Second, one should deal with the gain of the antennas and not their directivities, which is an alternate way of referring to the input power fed to the antennas rather than to the radiated power. The radiated power essentially deals with the directivity of an antenna and theoretically one can get any value for the directivity of an aperture but the gain is finite. Hence, the distinction needs to be made between gain and directivity if one is willing to compare system performances in a proper way. Finally, one needs to use the Poynting’s theorem to calculate the power in the near field and not exclusively use either the voltage or the current. These restrictions apply to the power form of the Shannon channel capacity theorem. The voltage form of the capacity due to Hartley is applicable to both near and far fields. Use of realistic antenna models in place of representing antennas by point sources further illustrates the above points, as the point sources by definition generate only far field, and they o not exist in real life.

 

The concept of a multiple-input-multiple-output (MIMO) antenna system is illustrated next and its strengths and weaknesses are outlined. Sample simulations show that only the classical phased array mode out of the various spatial modes that characterize spatial diversity is useful for that purpose and the other spatial modes are not efficient radiators. Finally, how reciprocity can be used in directing a signal to a preselected receiver when there is a two way communication between a transmitter and the receiver even in the presence of interfering objects is demonstrated. This embarrassingly simple method based on reciprocity, is much simpler in computational complexity than a traditional MIMO and can even exploit the polarization properties for effectively decorrelating multiple receivers in a multiple-input-single-output (MISO) system.


An Overview of Ultrawideband Antennas


Conventionally, the design of antennas is narrowband and little attention is paid to the phase responses of the devices as functions of frequency. Even the use of the term broadband is misleading as one essentially takes a narrow band signal and sweeps it across the band of interest. In fact, it is not necessary to pay too much attention to the phase for narrowband signals, as the role played by the frequency factor is that of a scalar multiplier. However, if one now wants to use multiple frequencies and attempts to relate the data obtained at each frequency, then this frequency term can no longer be ignored. Depending on the application, this scale factor can actually have significant variations, which also depend on the size and the shape of the bandwidth over which the performance of the system is observed. In the time domain, the effect of this frequency term creates havoc as it provides a highly nonlinear operation and hence must be studied carefully. By broadband we mean temporal signals with good signal integrity. When it comes to waveform diversity, which implicitly assumes time-dependent phenomena, it is not possible to do any meaningful system design unless the effects of the antennas are taken into account. These effects will be illustrated in terms of the responses of the antennas and on the applicability of the current popular methodology of time reversal for the vector electromagnetic problem.

 

To provide a background, notions of bandwidth will be discussed, especially in light of recent interest in ultrawideband (UWB) systems – the last decade has witnessed significantly greater interest in UWB radar. In that time, more than 15 nonmilitary UWB radars have been designed and fielded, which include applications to forestry, detecting underground utilities, and humanitarian demining. Since an antenna is an integral part of sensing systems, selected highlights of UWB antenna development will be very briefly summarized. It will also be illustrated how to design a discrete finite time domain pulse under the constraint of the Federal Communications Commission (FCC) ultra-wideband (UWB) spectral mask. This pulse also enjoys the advantage of having a linear phase over the frequency band of interest and is orthogonal to its shifted version of one or more baud time. The finite time pulse is designed by an optimization method and concentrates its energy in the allowed bands specified by the FCC. Finally, an example is presented to illustrate how these types of wideband pulses can be transmitted and received with little distortion.

 

Some fundamental problems in studying concepts involving the responses of antennas in the time domain are related to our subconscious definition of reciprocity. In the frequency domain, reciprocity is related simply to the fact that the spatial response of the sensor in the transmit mode is EQUAL to the spatial response of the sensor in the receive mode at any frequency of interest. In the time domain, the spatial response of the sensor will be time dependent. Hence, both the transmit and the receive impulse responses of the sensor will be a function of azimuth and elevation angles. However, for a fixed spatial angle, the transmit impulse response is NOT EQUAL to the receive impulse response of ANY sensor. In fact, mathematically one can argue that the transmit impulse response is the time derivative of the receive impulse response for any sensor. One may then conclude that somehow reciprocity is violated through this principle. The important fact is that the product in the frequency domain results in a convolution in the time domain and that the reciprocity relationship is no longer a simple one. Even though the transmit impulse response is the time derivative of the receive impulse response, reciprocity still holds! The above principle now helps us in characterizing different sensors for different applications as their temporal responses are quite different.

 

As a first example, it will be shown that an electrically large wide-angle biconical antenna on transmit does not distort the waveform, whereas on receive it does an integration of the waveform for certain conditions. In contrast, a TEM horn antenna on transmit differentiates the input waveform, whereas on receive it does not distort the waveform. Use of such transmit/receive antennas can actually produce channels with practically no dispersion. Experimental results covering GHz bandwidth signals will be provided to illustrate these methodologies. Examples regarding the impulse responses of other types of antennas, like the century bandwidth antenna, impulse radiating antenna, and the like will also be presented.


Who Is the Father of Electrical Engineering?

 

The Electromagnetic community makes a living out of Maxwell’s name. However, yet very few researchers really know what actually Maxwell did! The goal of this presentation is to make the point that Maxwell was one of the greatest scientist of the last century and he could be called so even if he did not do any work on Electromagnetic Theory. Sir James Jeans pointed out: In his hands electricity first became a mathematically exact science and the same might be said of other larger parts of Physics. He did develop almost all aspects of Electrical Engineering and can unambiguously be called the father of electrical engineering even if he did not work on electromagnetics!. He published five books and approximately 100 papers.


To start with, as Sir Ambrose Fleming pointed out how Maxwell provided a general methodology for the solution of Kirchoff’s laws as a ratio of two determinants. Maxwell also showed how a circuit containing both capacitance and inductance would respond when connected to generators containing alternating currents of different frequencies. He developed the phenomenon of electrical resonance in parallel to acoustic resonance developed by Lord Rayleigh. Maxwell provided a simpler mathematical expression for the wave velocity and group velocity again when reviewing a paper by Rayleigh On Progressive Waves.

 

Maxwell showed that between any four colors an equation can be found, and this is confirmed by experiments. Secondly, from two equations containing different colors a third may be obtained. A graphical method can be described, by which after fixing arbitrarily the position of three standard colors that of any other color can be obtained by experiments. Finally, the effect of red and green glasses on the color-blind will be presented, and a pair of spectacles having one eye red and the other green was proposed by him as assistance to detect doubtful colors. He was the first to show that in color blind people, their eyes are sensitive only to two colors and not to three as in normal eyes. Typically, they are not sensitive to red. He perfected the ophthalmoscope initially developed by Helmholtz to look into the retina. At the point of the retina where it is intersected by the axis of the eye there is a yellow spot, called the macula. Maxwell observed that the nature of the spot changes as a function of the quality of the vision. The macular degeneration of the eye affects the quality of vision and is the leading cause of blindness in people over 55 years old. Today, the extent of macular degeneration of the retina is characterized by Maxwell’s yellow spot test. He also developed the fish eye lens to look into the retina with little trauma. He provided a methodology for generating any color represented by a point inside a triangle whose vertices represented the three primary colors that he chose as red green and blue. However, as he demonstrated other choices for the primary colors are equally viable. The new color is generated by mixing the three primary colors in a ratio determined by the respective distance of the point representing the new color from the vertices of the triangle. In the present time, this triangle is called a chromatist diagram used in various movie and TV studios, and differs in details from his original. Maxwell asked Thomas Sutton (the inventor of the single lens reflex camera) to take the first color photograph of a Tartan ribbon. The experimental set up was to take three pictures separately using different colors and then project the superposed pictures to generate the world’s first color photograph. Today, color television works on this principle, but Maxwell’s name is rarely mentioned.

 

He established the electrostatic units and the electromagnetic units to setup a coherent system of units and presented a thorough dimensional analysis and thus put dimensional analysis on a scientific footing which was discovered much earlier by Fourier and others. The ESU and the EMU system of units were later mislabeled as the Gaussian system of units. He also introduced the dimensional notation which were to become the standard of using the powers of Mass, Length and Time. He also showed that the relation between the two units electromagnetic units, ESU and EMU, has a dimension LT–1, which has a value very close to that of velocity of light. Later on, he also made an experiment to evaluate this number.

 

He used polarized light to reveal strain patterns in mechanical structures and developed a graphical method for calculating the forces in the framework. He developed general laws of Optical instruments and even developed a comprehensive theory on the composition of Saturn’s rings. He also created a standard for electrical resistance.

 

When creating his standard for electrical resistance, he wanted to design a governor to keep a coil spinning at a constant rate. He made the system stable by using the idea of negative feedback. He worked out the conditions of stability under various feedback arrangements. This was the first mathematical analysis of control systems. He showed for the first time that for stability the characteristic equation of the linear differential equation has to have all its roots with negative real parts.

 

He not only introduced the first statistical law into physics but also introduced the concept of ensemble averaging which is an indispensable tool in communication theory and signal processing. His work on the mythical creature termed Maxwell’s demon lead to the quantization of certainty and led to the introduction of the notion of information content. He was a co-developer of the concept of entropy with Boltzmann which was expounded by Leo Szilard and twenty years later after that by Claude Shannon as information theory.

 

He laid the basic foundation for electricity, magnetism, and optics. He introduced the terms “curl”, “convergence” and “gradient”. Nowadays, the convergence is replaced by its negative, which is called “divergence”, and the other two are still in the standard mathematical literature. His name is primarily associated with the famous four equations called Maxwell’s equations. The crux of the matter is that Maxwell did not write those four equations that we use today. Starting from Maxwell’s work, they were first put in the scalar form by Heinrich Hertz and in the vector form by Oliver Heaviside, who did not even have a college education! This is why Einstein used to call them the Maxwell-Hertz-Heaviside equations.

 

The goal of this presentation is to illustrate those points and finally what exactly did Maxwell do to come to the conclusion that light was electromagnetic in nature. In summary, the reason why Maxwell’s theory was not accepted for a long time by contemporary physicists was that there were some fundamental problems with his theory. Also, it is difficult to explain what those problems were, using modern terminology. As Maxwellian theory cannot be translated into familiar to the modern understanding because the very act of translation necessarily deprives it of its deepest significance and it was this significance which guided research. The talk will explain what was the problem and Maxwell really mean by the Displacement current!

 

He was the joint scientific editor of the 9th edition of Encyclopedia Britannica. There he provided an account of the motion of earth through ether. Maxwell suggested that ether could perhaps be detected by measuring the velocity of light when light was propagated in opposite directions. He had further discussions in a letter to David Peck Todd, an astronomer at Yale. Maxwell’s suggestion of a double track arrangement led A. A. Mickelson, when he was working under Helmholtz as a student, to undertake his famous experiments later on ether drag in 1880’s and the rest is history.


Maxwell always delivered scientific lectures for the common people using models. Even though Maxwell has influenced development in many areas of physical sciences and had started a revolution in the way physicists look at the world, he is not very well known, unfortunately, outside some selected scientific communities. The reasons for that will also be described, which perhaps may be embedded in his prolific writing of limericks, as we will see.


Solving Challenging Electromagnetic Problems using MoM and a Parallel Out-Of-Core Solver

 

The Method of Moments (MoM) is a numerically accurate method for electromagnetic field simulation for antenna and scattering applications. It is an extremely powerful and versatile general numerical methodology for discretizing integral equations to a matrix equation. However, traditional MoM with sub-domain basis function analysis is inherently limited to electrically small and moderately large electromagnetic structures because its computational costs (in terms of memory and CPU time) increase rapidly with an increase in the electrical size of the problem. The use of entire-domain basis functions in a surface integral equation may still be the best weapon available in today’s arsenal to deal with challenging complex electromagnetic analysis problems. Even though higher-order basis functions reduce the CPU time and memory demands significantly, it is still critical to maximize performance to be able to solve problems as large as possible.

 

Single processor computers of the past were generally too small to be able to handle the problems which need to be solved today. Single-core processors used the IA-32 (Intel Architecture) instruction set. The 32-bit architecture addressing restricts the size of the variable which can be stored in memory to a limit of 2 GB for most operating systems. The matrix size is therefore constrained to approximately 15,000X15,000 when the variable is defined in single precision and to approximately 11,000X11,000 when using double precision arithmetic. The IA-32 structure was extended by Advanced Micro Devices (AMD) in 2003 to 64 bits, although keeping the same nomenclature. A 64-bit computer, can theoretically address 263 9.2 million Terabytes directly, which corresponds to the solution of a 109 X 109 matrix in single precision or a 0.76*109 X 0.76*109 matrix in double precision, provided enough physical and virtual memory are available. Support of memory addressing is still limited by the bandwidth of the bus, the operating system and other hardware and software considerations. The price of large-size memory is very high and usually dominates the budget for the whole computer system for MoM EM solvers. Such a large amount of RAM is too expensive to be affordable for most research institutes.

 

In recent years, due to thermal issues, single-core processor technology has been abandoned for new developments in multi-core processors. CPU speed has been sacrificed for thermal efficiency, with multi-core processor speeds greatly reduced from their single-core predecessors, by as much as 50%. No longer will numerical codes be able to benefit from continually higher processing speeds. So how will numerical codes advance in light of these technological changes? That is the crux of the research presented here.

 

How can we expand the capability and power of the numerically accurate MoM code to achieve the goal of solving a million by million unknown problem? Such a large sized problem would require 16 Terabytes of storage. Purchasing RAM of that size is not practical because of the cost. However, the large matrix can be written to the hard disk. Presently, hard disks can be quite large, say 500 GB to 1 TB each, and can be cascaded in RAID-0 configuration. The problem in writing to the hard disk is that it is typically considered to be much slower than writing to the RAM.

 

The parallel out-of-core integral equation solver can break through memory constraints for a computer system by enabling efficient accessing of hard disk resources and fast computational speed. It can run on a desktop with multiple single-core or multi-core processors by simply assigning one message passing interface (MPI) process to execute the software on each core. It can similarly be executed on high performance computing clusters with hundreds or thousands of servers, each with multiple multi-core CPUs. On a Beowulf network of workstations with 50 processors, a dense complex system of equations of order 40,000, may need only about two hours to solve. This suggests that the processing power of high performance machines is under-utilized and much larger problems can be tackled before run time becomes prohibitively large.

 

The main challenge is that if the parallelization of the code is not done appropriately for the hardware under consideration, the result will be an extremely inefficient code as the clock speed of future chips decreases with increasing number of cores. The key is to reduce latency and obtain proper load balancing so that all the cores are fully utilized. The research presented here provides a road map through the jungle of new technology and techniques. The map is illustrated with results obtained on an array of computational platforms with different hardware configurations and operating system software.

 

In the first step, parallelization of the impedance matrix generation should produce a linear speedup with increasing number of processes. If the parallelization is done in an appropriate fashion, this linear speedup will be evident. Distributing the computation of the elements of the matrix enables a user to solve very large problems in reasonable time. Since the matrix generated by MoM is a full dense matrix, the LU decomposition method used to solve the matrix equation is computationally intensive when compared with the read/write process of accessing the hard disk I/O.

 

The second step for the solution of this distributed matrix stored on the various processors is how to implement the LU decomposition. The basic mechanism of an out-of-core (OOC) solver is to write the large impedance matrix onto the hard disk, read into memory a part of it for computation, and write the intermediate results back to the hard disk when the computation of the part is done. When a parallel OOC is used as a solver, each out-of-core matrix is associated with a device unit number, much like the familiar Fortran I/O subsystem.

 

Even though the servers may be connected by 10/100M network adapters in a cluster, over 75% parallel efficiency still can be achieved. Examples will be presented to illustrate the solution of extremely large problems, such as analyzing targets in their natural environments. Comparison with experimental data will be shown to demonstrate that accuracy of the solution is maintained in solving electrically very large and complex problems.

 

This talk will describe the various principles involved in using MoM with higher-order basis functions, and using parallel out-of-core algorithms for the solution of complicated EM problems encountered in the real world. The talk will start by explaining a load balanced parallel MoM matrix filling scheme by using MPI virtual topology. The principles of ScaLAPACK in an out-of-core scenario will be described and illustrated such that even for extremely large problems the penalty for using an out-of-core solver over an in-core one may be of the order of 30%. This is in contrast to the long execution time encountered when using the built-in virtual memory mode of operating systems. Finally, plots will be presented to illustrate the principle of load balancing to keep the communication between cores to a minimum, resulting in a highly efficient code which is capable and flexible enough to be used on a single desktop PC, a collection of workstations, or a high performance computing cluster.

 

The combination of MoM accuracy, hard disk capacity and parallel OOC solver efficiency results in a powerful tool capable of handling the challenging demands of 21st century antenna and radar communities.

 

An Exposition on the Choice of the Proper S-Parameters in Characterizing Devices Including Transmission Lines with Complex Reference Impedances and a General Methodology to Compute them


The purpose of this paper is to demonstrate that a recently published paper dealing with little known facts and some new results on transmission lines is due to an incomplete interpretation of the nonphysical artifacts resulting from a particular mathematical model for the S-parameters. These artifacts are not real and do not exist when a different form of the S-parameters are used. Thus, the first objective of this paper is to introduce the two different types of S-parameters generally used to characterize microwave circuits with lossy characteristic impedance. The first one is called the pseudo-wave, an extension of the conventional travelling wave concepts, and is useful when it is necessary to discuss the properties of a microwave network junction irrespective of the impedances connected to the terminals. However, one has to be extremely careful in providing a physical interpretation of the mathematical expressions as in this case the reflection coefficient can be greater than one, even for a passive load impedance and the transmission line is conjugately matched. Also, the power balance cannot be obtained simply from the powers associated with the incident and reflected waves. The second type of S-parameters is called the power wave scattering parameters. They are useful when one is interested in the power relation between microwave circuits connected through a junction. In this case, the magnitude of the reflection coefficient cannot exceed unity and the power delivered to the load is directly given by the difference between the powers associated with the incident and the reflected waves. Since this methodology deals with the reciprocal relations between powers from various devices this may be quite suitable for dealing with a pair of transmitting and receiving antennas where power reciprocity holds. This methodology is also applicable in network theory where the scattering matrix of a two port (or a multiport) can be defined using complex reference impedances at each of the ports without any transmission line being present, so that the characteristic impedances become irrelevant. Such a situation is typical in small signal microwave transistor amplifiers, where the analysis necessitates the use of complex reference impedances in order to study simultaneous matching and stability. However, for both the definition for the S-parameters, when the characteristic impedance or the reference impedance is complex, the scattering matrix need not be symmetric even if the network in question is reciprocal.

 

The second objective is to illustrate that when the characteristic impedance of the line or the reference impedances in question is real and positive, then both of them provide the same results. Finally, a general methodology with examples is presented to illustrate how the S-parameters can be computed for an arbitrary network without any a priori knowledge of its characteristic impedance.




 

2012-2014

 

Prof. Kwok Wa Leung
Department of Electronic Engineering
City University of Hong Kong
83 Tat Chee Avenue, Kowloon Tong
Kowloon, Hong Kong

eekleung@cityu.edu.hk

 

Kwok Wa Leung was born in Hong Kong. He received the B.Sc. degree in Electronics and Ph.D. degree in electronic engineering from the Chinese University of Hong Kong, in 1990 and 1993, respectively.

 

From 1990 to 1993, he was a Graduate Assistant with the Department of Electronic Engineering, the Chinese University of Hong Kong. In 1994, he joined the Department of Electronic Engineering at City University of Hong Kong (CityU) and is currently a Professor and an Assistant Head of the Department. He is also the founding Director of the Innovation Centre of the Department. From Jan. to June, 2006, he was a Visiting Professor in the Department of Electrical Engineering, The Pennsylvania State University, USA.


Professor Leung was the Chairman of the IEEE AP/MTT Hong Kong Joint Chapter for the years of 2006 and 2007. He was the Chairman of the Technical Program Committee, 2008 Asia-Pacific Microwave Conference, Hong Kong, the Co-Chair of the Technical Program Committee, 2006 IEEE TENCON, Hong Kong, and the Finance Chair of PIERS 1997, Hong Kong. His research interests include RFID tag antennas, dielectric resonator antennas, microstrip antennas, wire antennas, guided wave theory, computational electromagnetics, and mobile communications. He was an Editor for HKIE Transactions and a Guest Editor of IET Microwaves, Antennas and Propagation. Currently, he serves as an Associate Editor for IEEE Transactions on Antennas and Propagation and received Transactions Commendation Certificates twice in 2009 and 2010 for his exceptional performance. He is also an Associate Editor for IEEE Antennas and Wireless Propagation Letters. He has been appointed as a Distinguished Lecturer by the IEEE Antennas and Propagation Society for 2012-2014.


Professor Leung received the International Union of Radio Science (USRI) Young Scientists Awards in 1993 and 1995, awarded in Kyoto, Japan and St. Petersburg, Russia, respectively. He received Departmental Outstanding Teacher Awards in 2005, 2010, and 2011. He is a Fellow of IEEE and HKIE.

 

Development of the Dielectric Resonator Antenna


The fundamentals and development of dielectric resonator antenna will be discussed in this talk. For many years, dielectric resonators (DRs) have only been used as high-Q elements in microwave circuits until S. A. Long and his collaborators showed that they can also be used as efficient radiators. The studies were motivated by an observation that carrier frequencies of modern wireless systems had gradually progressed upward to the millimeter-wave region, where efficiencies of metallic antennas can be reduced significantly due to the skin effect. In contrast, DR antennas (DRAs) are purely made of dielectric materials with no conductor loss. This feature makes DRAs very suitable for millimeter-wave systems.

 

As compared to the microstrip antenna, the DRA has a much wider impedance bandwidth (~ 10 % for dielectric constant ~ 10). This is because the microstrip antenna radiates only through two narrow radiation slots, whereas the DRA radiates through the whole DRA surface except the grounded part. Avoidance of surface waves is another attractive advantage of the DRA over the microstrip antenna. Nevertheless, the DRA and microstrip antenna have many common characteristics because both of them are resonators. For example, both of them can be made smaller in size by increasing the dielectric constant because the dielectric wavelength is smaller than the free-space wavelength. Furthermore, basically all excitation methods applicable to the microstrip antenna can be used for the DRA.

 

Although the DRA received attention originally for millimeter-wave applications, it is also widely investigated at microwave or even RF frequencies. It is because the DRA is a volume device that offers designers more degrees of freedom than 2D-type antennas (e.g., microstrip antennas) or 1D-type antennas (e.g., monopole antennas). Other advantages of the DRA include its light weight, low cost, low loss, and ease of excitation.

 

The following DRA topics will be covered in this talk:
                 

  • Basic theory
  • Frequency-tuning techniques
  • Circularly polarized DRAs
  • Dualband and wideband DRAs
  • Dualfunction DRAs
  • Omnidirectional DRAs
  • Higher-order-mode DRAs

 


Transparent Antennas: From 2D to 3D

 

Transparent antennas are very attractive. They can be integrated with clear substrates such as window glass, or with solar cells to save surface areas of satellites. Transparent antennas are normally realized using (2D) planar structures based on the theory of patch antenna. The optical transparency can be obtained by fabricating meshed conductors or transparent conductors on an acrylic or glass substrate. Transparent designs using the meshed-conductor approach are straightforward because optical signals can pass through the opening of the meshes, while microwave signals can be transmitted or received by the conductors. The transparency and antenna property can be optimized by refining the width of the mesh. In this talk, results of a transparent antenna with meshed conductors will be presented.

 

In the transparent-conductor approach, transparent conductive films are used as radiators. Commonly used transparent conductive films include indium tin oxide (ITO), silver coated polyester film (AgHT), and fluorine-doped tin oxide (FTO). A sheet resistance of at least 1-2 ohm/square is required to obtain an optical transmittance of better than 70%. However, antennas made of such transparent conductor films are not efficient because of the high sheet resistance. This is one of the major obstacles to the widespread application of transparent antennas. A method that alleviates this problem will be discussed in this talk.

 

For a long time, transparent antennas have been of planar (2D) structures. Very recently, 3D transparent antennas have also been developed. This is a new topic. The principle of 3D transparent antenna is based on the theory of dielectric resonator antenna; the resonance is caused by the whole 3D structure rather than a confined cavity as found in the patch-antenna case. For glass, it is usually assumed that its refractive index is ~1.5, giving a dielectric constant of ~ 2.25. This value is too low for a DRA to have good polarization purity. However, it was generally overlooked that this dielectric constant was obtained at optical frequencies instead of microwave frequencies. Recently, a dielectric constant of ~7 was measured for glass at 2 GHz and this value is sufficient for obtaining a good radiator. Since crystals are basically glass, they can also be used for antenna designs. In this talk, the characteristics of glass DRAs will be shown. In addition, the idea of using a 3D glass antenna as a light cover will be presented. It has been experimentally found that the lighting and antenna parts do not affect each other because they are operating in totally different frequency regions. Interesting results will be presented in this talk.

 

Finally, it will be shown that 3D transparent antennas can be designed as aesthetic glass (or crystal) wares or artworks. This idea is especially useful when invisible antennas are needed due to psychological reasons. The idea has been demonstrated successfully using a glass swan and apple bought from the commercial market. The results will be presented in this talk.


Analyses of Spherical Antennas


The spherical antenna is an interesting and useful topic. For example, a spherical helical antenna can radiate circularly polarized fields over a wide beamwidth. An antenna array with its elements distributed over a spherical surface is able to determine the direction-of-arrival and polarization of an incoming wave. Further, a spherical antenna array can be used to avoid the scanning problem of a planar array at low elevation.

 

The spherical antenna is also important from the theoretical point of view. Since a spherical structure does not have any edge-shaped boundaries as found in cylindrical and rectangular structures, its closed-form Green’s function is obtainable. As a result, an exact solution of a spherical problem can exist, and the solution can be used as a reference for checking the accuracy of numerical or approximation techniques.

 

In this talk, the general solution of Helmholtz equation in the spherical coordinates will be briefly reviewed. The solution will be used to solve different spherical antenna problems, including the spherical slot antenna, spherical microstrip antenna, and grounded hemispherical dielectric resonator antenna (which is equivalently a dielectric sphere after imaging). Derivations of their exact modal Green’s functions will be described. Both electric and magnetic current sources will be considered, and their integral equations will be formulated using the Green’s functions. The method of moments (MoM) will be used to solve for the electric or magnetic current sources. From the currents, the input impedances and radiation patterns of the spherical antennas can be obtained easily.

 

When a field point coincides with a source point, the Green’s functions will become singular and care has to be exercised in evaluating their MoM integrals. Around a singular point, an extensive number of modal terms are needed to calculate the Green’s functions accurately. This may lead to practical problems because amplitudes of high-order Hankel functions can be too large to be handled numerically. A method that tackles the singularity problem will be presented. In this talk, integrals involving spherical Bessel functions or associate Legendre functions will be evaluated rigorously through analytical integration or their recurrence formulas. Since numerical integration is avoided, the evaluations of the integrals are computationally very efficient. Numerical convergence of the modal solutions will also be examined. Excellent agreement between theory and experiment is observed and the results will be presented in the talk. Finally, it will be shown that a spherical solution can be used to solve a planar annular problem.



Stefano Maci

Professor of Electromagnetics and Antennas

Department of Information Engineering

University of Siena

Via Roma 56, 53100, Sienna Italy

390 577 2346235

macis@dii.unisi.it

 

Stefano Maci is a Professor the University of Siena (UNISI), with scientific responsibility of a group of 15 researchers (http://www.dii.unisi.it/~lea/).  He is the Director of the UNISI PhD School of Information Engineering and Science, which presently includes about 60 PhD students. His research interests include high-frequency and beam representation methods, computational electromagnetics, large phased arrays, planar antennas, reflector antennas and feeds, metamaterials and metasurfaces.

 

Since 2000, he was responsible of 5 projects funded by the European Union (EU); in particular, in 2004-2007 he was WP leader of the Antenna Center of Excellence (ACE, FP6-EU) and in 2007-2010 he was International Coordinator of a 24-institution consortium of a Marie Curie Action (FP6). He also carried out several projects supported by the European Space Agency (ESA-ESTEC), the European Defense Agency (EDA), the US-Army Research Laboratory (ARL), and by various industries and research institutions: EADS-MATRA, (Tolosa, Francia), IDS (Pisa, Italia), TICRA (Copenhagen), ALENIA MARCONI SYSTEM (Rome, Italy), SAAB-ERICSON SPACE (Gotheborg, Svezia), THALES (Paris, France), TNO (L'Aia, Olanda), OTO MELARA (La Spezia, Italia), OFFICINE GALILEO (Florence, Italy), SELEX Communication (Rome), Thales Alenia Space (Rome).

 

Since 2001 he was a member the Technical Advisory Board of 11 international conferences, member of the Review Board of 6 International Journals; in the same period, he organized 23 special sessions in international conferences, and he held 10 short courses in the IEEE Antennas and Propagation Society (AP-S) Symposia about metamaterials, antennas and computational electromagnetics. He was an Associate Editor of IEEE Trans on EMC and of IEEE Trans. on AP and two times Guest Editor of special issues of the latter journal. In 2003 he was elected Fellow of IEEE.

 

In 2004 he founded the European School of Antennas (ESoA), a PhD school that presently comprises 30 courses on Antennas, Propagation, Electromagnetic Theory, and Computational Electromagnetics. ESoA counts about 150 among the best teachers of Europe (which include eleven IEEE Fellows) and it is frequented by an average of 220 students per year. The ESoA consortium presently comprises 33 European research centers and offers 12 one-week courses per year.

 

In 2005-2007, he was Italian National representative of the NATO SET-TG 084 "Emerging Technology for Sensor and Front-ends”, and he is presently involved as co-representative in the NATO SET-181 RTG on "Metamaterials for Defense and Security Applications".
Stefano Maci was co-founder of two spinoff-companies and since 2008 he is honorary President of LEAntenne e Progetti SPA (Valeggio sul Mincio, VE).

 

Stefano Maci is presently Director of ESoA, a member of the Board of Directors of the European Association on Antennas and Propagation (EuRAAP), a member of the Technical Advisory Board of the URSI Commission B, a member elected of the AdCom of IEEE Antennas and Propagation Society, a member of the Governing Board of the European Science Foundation (ESF) Project “NewFocus”, a member of the Governing board of the FP7 coordination action “CARE” (Coordinating the Antenna Research in Europe), a member of the Award Committee of the IEEE Antennas and Propagation Society (AP-S), a member of the Antennas and Propagation Executive Board of the Institution of Engineering and Technology (IET, UK), and a member of the Focus Group on METAMATERIALS in the Finmeccanica project “Mind-Share”.  

His research activity is documented in 10 book chapters, 110 papers published in international journals, (among which 76 on IEEE journals), and about 300 papers in proceedings of international conferences. His h index is 24, with a record of more than 2000 citations (source Google Scholar).


 

Metasurfing Wave Antennas


Metasurfaces constitute a class of thin metamaterials, which can be used from microwave to optical frequencies to create new electromagnetic engineering devices. They are obtained by a dense periodic texture of small elements printed on a grounded slab without or with shorting vias. These have been used in the past for realizing electromagnetic bandgaps (EBG) or equivalent magnetic-walls. Changing the dimension of the elements, being the sub-wavelength 2D-periodicity equal, gives the visual effect of a pixelated image and the electromagnetic effect of a modulation of the equivalent local reactance. The modulated metasurface reactance (MMR) so obtained is able to transform surface or guided waves into different wavefield configurations with required properties. This MMR-driven wavefield transformation is referred to as “Metasurfing”. The MMR allows in fact a local modification of the dispersion equation and, at constant operating frequency, of the local wavevector. Therefore, the general effects of metasurface modulation are similar to those obtained in solid (volumetric) inhomogeneous metamaterial as predicted by the Transformation Optics; namely, re-addressing the propagation path of an incident wave. However, significant technological simplicity is gained.

 

When the MMR is covered by a top ground plane (Parallel-plate waveguide Metasurfing) the real part of the Poynting vector follows a generalized Fermat principle as happen in ray-field propagation in inhomogeneous solid medium. This may serve for designing lenses or point-source driven beam-forming networks. When the MMR is uncovered, wave propagation is accompanied by leakage; i.e., a surface wave is transformed into a leaky-wave, and the structure itself becomes an extremely flat antenna. In every case, introducing slots in the printed elements allows a polarization control. In such cases, the metasurface associated with can be described by an anisotropic surface impedance. 

 

In this lecture, after illustration of the design method of metasurfing-wave antennas, various examples are presented and discussed, including Luneburg lenses, Maxwell’s Fish-eyes, isoflux antennas, Doppler-guide antennas and new transmission lines.        

 

Retrieval of Constitutive Parameters in Metamaterials

The amazing interest on metamaterials, which has been growing for a decade, has in parallel posed a lot of questions about the most reliable and accurate approach to the characterization of their electromagnetic behavior.  Most of the metamaterials can be described as a periodic repetition of some inclusions in a host medium; the inclusions can be made resonant despite their small dimension in terms of a wavelength. It is well accepted in various scientific communities to consider this type of artificial structures as effective media, described by a set of equivalent constitutive parameters. These parameters can be obtained by using analytical models, measurements or full-wave simulations in conjunction with numerical retrieval algorithms. However, the procedure for the definition of the equivalent parameters is not univocally defined, and different approaches may be used depending on the metamaterial characteristics and on the goal of the homogenization process.


The analysis methodologies for retrieval of constitutive parameters include those based on a microscopic-equivalence and those based on a macroscopic-equivalence. The former set up a model relating each element of the periodic arrangement to an equivalent particle with electric and/or magnetic dipolar moment. This requires constituent particles small in terms of a wavelength, since the response of the single particle is approximated by the dominant term of a multi-polar expansion. On the other hand, macroscopic-equivalence approaches identify equivalent wave impedance and propagation constant for the field propagating inside the metamaterial, and they look for a homogeneous medium supporting the same modal structure. In this case the restrictions on the electrical size of the inclusion may be less severe, and it is possible to correctly retrieve the scattering parameters from a metamaterial sample. However, there could be some intrinsic ambiguities in the extraction of the equivalent parameters.

 

In this lecture, after the review of the literature, an original method of retrieval of the metamaterial constituent parameters is described, with emphasis on removing ambiguity and on the role played by the spatial dispersivity of the constituent parameters. The special class of metamaterials formed by periodic multilayer arrangements of 2D printed structures will be considered with much attention. Anisotropy and special case of gyrotropy, as well as bianisotropy and the special case of chirality will be considered in the parameter retrieval.

 

Scattering Matrix Domain Decomposition Method Formalized with Different Wave Propagators

In most of the real applications, antennas need to be located in a complex operative environment;  accurate analysis is needed to take into account interaction with antenna platform or other surrounding antennas. A rigorous numerical analysis of these large problems is a very complex task, due to the prohibitive number of unknowns; furthermore, the simultaneous presence of electrically large structures and small features may lead to ill conditioning.

 

The Domain Decomposition Method is a general approach for the solution of complex multiscale problems, which allows one to overcome the above mentioned impairments; it consists in dividing the original problem into simpler, more tractable non-overlapped subdomains that are solved separately, and then obtaining the overall solution by imposing proper connections among different subdomains. In particular, if the sub-domains boundaries are associated with ports through which a proper set of modes flow, the interactions among different sub-domains can be rigorously described through an equivalent network representation. Depending on the propagation mechanism within each sub-domain, different types of modes or ”wave objects” can be used. In particular, beam-type fields or radiated modes are conveniently used when dealing with radiation and scattering problems, while waveguide modes are well suited for representing guided waves.

 

Different choices of the wave objects used for field representation lead to different implementations of the generalized network formulation. The optimal choice is the one maximizing the efficiency of the overall numerical analysis, and depends on the problem under consideration. In this talk, two particular implementations are considered: the first one uses complex point source (CPS) beams  as wave objects, while the second one uses spherical waves (SW) for the representation of radiated field and waveguide modes at the antenna input port. In the first case, thanks to the angular selectivity of the CPS beams, only a small fraction of the beams contribute to the subdomain interactions, thus, leading to an efficient numerical procedure. In the second case, the choice of spherical waves offers the advantage of direct interfacing with the output of spherical near-field measurements or numerical simulations, while the inclusion of waveguide modes provides the information about the reflection coefficient at the antenna input port.

 


Dr. Brian M. Kent , ST
Chief Scientist, Sensors Directorate
Air Force Research Laboratory
Wright-Patterson Air Force Base, Ohio 45433-7130
Brian.kent@wpafb.af.mil
kentbmoh@woh.rr.com

 

Dr. Brian M. Kent, a member of the scientific and professional cadre of senior executives, is Chief Scientist, Sensors Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio. He serves as the directorate's principal scientific and technical adviser and primary authority for the technical content of the science and technology portfolio. He evaluates the total laboratory technical research program to determine its adequacy and efficiency in meeting national, Department of Defense, Air Force, Air Force Materiel Command and AFRL objectives in core technical competency areas. He identifies research gaps and analyzes advancements in a broad variety of scientific fields to advise on their impact on laboratory programs and objectives. He recommends new initiatives and adjustments to current programs required to meet current and future Air Force needs. As such, he is an internationally recognized scientific expert, and provides authoritarian counsel and advice to AFRL management and the professional staff as well as to other government organizations. He also collaborates on numerous interdisciplinary research problems that encompass multiple AFRL directorates, customers from other DOD components, as well as the manned space program managed by NASA. 

Dr. Kent joined the Air Force Avionics Laboratory in 1976 as cooperative engineering student through Michigan State University. He began his career performing research in avionics, digital flight displays and radar signature measurements. Through a career broadening engineering assignment with the Directorate of Engineering, Aeronautical Systems Division, he modeled a number of foreign threat missile systems and performed offensive and defensive electronic combat systems assessments. He received a National Science Foundation Fellowship in 1979, working at both the Air Force Wright Aeronautical Laboratories and the Ohio State University Electroscience Laboratory until the completion of his doctorate. Dr. Kent spent two years in the Passive Observables Branch of the Avionics Laboratory, later transferring to the AFWAL Signature Technology Office. From 1985 to 1992, Dr. Kent was involved with classified research efforts, managed through the Air Force Wright Laboratory, now the AFRL. During his tenure with AFRL and its predecessor organizations, Dr. Kent held a variety of positions. He has made pioneering and lasting contributions to the areas of signature measurement technology, and successfully established international standards for performing radar signature testing.

Dr. Kent has authored and co-authored more than 85 archival articles and technical reports and has written key sections of classified textbooks and design manuals. He has delivered more than 200 lectures, and developed a special DOD Low Observables Short Course that has been taught to more than 2,000 scientists and engineers since its inception in 1989. Dr. Kent has provided technical advice and counsel to a wide range of federal agencies, including the Department of Transportation, the Department of Justice and NASA's Space Shuttle Program. He is also an international technical adviser for the DOD and has provided basic research guidance to leading academic institutions.

 

Contributions of the US Air Force Laboratory’s Sensor’s Directorate to the Columbia Accident Investigation - shedding light on the mystery of the flight day two object and our role in returning the Shuttle to safe flight.


In the wake of the Columbia tragedy, Air Force Space Command carefully reviewed records of all radar objects in space during the time the Shuttle was on orbit. To everyone’s surprise, a post accident review revealed that a mysterious object separated from the Orbiter on Flight Day 2 and subsequently de-orbited 60 hours later, burning up on re-entry. Reentry ballistics revealed an estimate of the object’s area to mass. Four ground based tracking radars gave a hint of the objects radar cross section at the UHF frequency of 433 MHz. The Columbia Accident Investigation Board (CAIB) wanted to know what the object was, and whether it could be related to the accident.  Three weeks after the accident, the CAIB eventually contacted Dr Brian Kent of the Air Force Research Laboratory Multi-spectral Advanced Compact Range measurement facility, for their help in assessing the mysterious object.  For the next two months, RCS measurements performed at the AFRL advanced compact range ultimately narrowed the mystery of the Flight Day 2 object to a very few possibilities. Their work became so visible that Dr Kent provided public testimony to the CAIB on May 6, 2003.  In light of the accident cause, NASA made many changes to the Shuttle system and supporting ground sensors. Dr Kent was involved in the fielding of a debris radar system that allows NASA to closely monitor ascent debris from ascending rockets, including the Shuttle. Come hear how a solid engineering analysis, good teamwork, and a bit of sleuthing shed light on what turned out to be one of the most intriguing issues in the Columbia investigation, leading eventually to returning the Shuttle to operational flight status.

 

Air Force Research Laboratory Sensors Directorate: An Update on the organization, Our Major Research Interests, and On-going Laboratory Construction and Modernization Activities


The AFRL Sensor Directorate mission is to “Lead the discovery, development, and integration of affordable sensor and countermeasure technologies for our warfighters.” Sensors is being transformed by a $45M military construction office and laboratory modernization effort related to consolidating our research workforce and laboratories from Rome, New York and Hanscom AFB, Massachusetts. This talk will outline Sensors vision for the future work in antenna design, multi-input/multi-output passive and active RF systems, and other research interests of the US Air Force. We will also describe the major new Sensors laboratory facilities recently completed, and provide insight into collaborative research opportunities.

 

Electro-Magnetic Interference Measurements on the Shuttle Orbiter "Discovery" in Preparation for Return to Flight - A Case Study


As NASA prepared the Space Shuttle for its first return to flight mission (STS-114) in the July 2005 timeframe, a number of new visual and radar sensors were used during the critical ascent phase of the flight to assess whether any unintentional debris was liberated from the Shuttle as it raced into orbit. New high-resolution C-Band and X-Band radars were used to help ascertain the location and speed of any released debris, and were also used to monitor routine flight events such as Solid Rocket Booster (SRB) separation. To assure these new radars did not interfere with flight-critical engine subsystems, an Electromagnetic Interference (EMI) measurement was performed on the Shuttle Orbiter "Discovery" in January 2005, using the Air Force Research Laboratory's Mobile Diagnostic Laboratory (MDL). This portable EM Measurement system performed a large number of attenuation measurements the night of January 17-18, 2005. This paper describes how the attenuation data was acquired, and the methodology used to reduce the data to predict average attenuation of the radar energy from the outside world to the inside of the aft engine bay of the Orbiter. This data, when combined with a separate NASA performed equipment level EMI analysis, demonstrated the new C and X-Band Debris Radars could be operated without adversely interfering with the Orbiter electronic systems in the aft avionics and engine bays.

 

Characterization of Space Shuttle Ascent Debris Based on Radar Scattering and Ballistic Properties --Evolution of the NASA Debris Radar System told in two parts


This is a two-part presentation (with break) that introduces the NASA Debris Radar (NDR) system developed to characterize debris liberated by the space shuttle (and any follow-on rocket system) during its ascent into space.  Radar technology is well suited for characterizing shuttle ascent debris, and is especially valuable during night launches when optical sensors are severely degraded.  The shuttle debris mission presents challenging radar requirements in terms of target detection and tracking, minimum detectable radar cross-section (RCS), calibration accuracy, power profile management, and operational readiness.  In Part I, I describe the NDR system consists of stationary C-band radar located at Kennedy Space Center (KSC) and two X-band radars deployed to sea during shuttle missions.  To better understand the signature of the shuttle stack, Xpatch calculations were generated at C and X band to predict the radar signature as a function of launch time.  These calculations agreed very well with measured data later collected.  Various sizes, shapes, and types of shuttle debris materials were characterized using static and dynamic radar measurements and ballistic coefficient calculations.  After a break, Part II discusses the NASA Debris Radar (NDR) successes, which led to a new challenge of processing and analyzing the large amount of radar data collected by the NDR systems and extracting information useful to the NASA debris community.  Analysis tools and software codes were developed to visualize the shuttle metric data in real-time, visualize metric and signature data during post-mission analysis, automatically detect and characterize debris tracks in signature data, determine ballistic numbers for detected debris objects, and assess material type, size, release location and threat to the orbiter based on radar scattering and ballistic properties of the debris. Future applications for space situational awareness and space-lift applications will also be discussed.

 

Dynamic Radar Cross Section and Radar Doppler Measurements of Commercial General Electric Windmill Power Turbines -- Predicted and Measured Radar Signatures


Commercial windmill driven power turbines (“Wind Turbines”) are expanding in popularity and use in the commercial power industry since they can generate significant electricity without using fuel or emitting carbon dioxide “greenhouse gas”.  In-country and near-off shore wind turbines are becoming more common on the European continent, and the United States has recently set long term goals to generate 10% of national electric power using renewable sources. In order to make such turbines efficient, current 1.5 MW wind turbine towers and rotors are very large, with blades exceeding 67 meters in diameter, and tower heights exceeding 55 meters.    Newer 4.5 MW designs are expected to be even larger. The problem with such large, moving metallic devices is the potential interference such structures present to an array of civilian air traffic control radars. A recent study by the Undersecretary of Defense for Space and Sensor Technology acknowledged the potential performance impact wind turbines introduce when sited within line of site of air traffic control or air route radars. In the Spring of 2006, the Air Force Research Laboratory embarked on a rigorous measurement and prediction program to provide credible data to national decision makers on the magnitude of the signatures, so the interference issues could be credibly studied. This paper will discuss the calibrated RCS and Doppler measurement of the turbines and compare this data (with uncertainty) to modeled data.

 


Dr. Monai Krairiksh
King Mongkut’s Institute of Technology Ladkrabang
Bangkok 10520, Thailand
kkmonai@kmitl.ac.th

 

Monai Krairiksh was born in Bangkok, Thailand. He received the B.Eng., M.Eng. and D.Eng. degrees from King Mongkut’s Institute of Technology Ladkrabang (KMITL), Thailand in 1981, 1984, and 1994, respectively.

He was a visiting research scholar at Tokai University in 1988 and at Yokosuka Radio Communications Research Center, Communications Research Laboratory (CRL) in 2004. He joined the KMITL and is currently a Professor at the Department of Telecommunication Engineering. He has served as the Director of the Research Center for Communications and Information Technology during 1997-2002. His main research interests are in antennas for mobile communications and microwave in agricultural applications.

Dr.Krairiksh was the chairman of the IEEE MTT/AP/Ed joint chapter in 2005 and 2006. He served as the General Chairman of the 2007 Asia-Pacific Microwave Conference, and the advisory committee of the 2009 International Symposium on Antennas and Propagation. He was the President of the Electrical Engineering/ Electronics, Computer, Telecommunications and Information Technology Association (ECTI) in 2010 and 2011 and was an editor-in-chief of the ECTI Transactions on Electrical Engineering, Electronics, and Communications.

He was recognized as a Senior Research Scholar of the Thailand Research Fund in 2005 and 2008 and a Distinguished Research Scholar of the National Research Council of Thailand.

 

Remote Sensing of the Physical Qualities of Fruits


Nondestructive determination of dielectric properties of materials is essential in various applications to monitor the nature of an object. Apart from many techniques like near infrared (NIR), X-ray, ultrasonic, and so on, a microwave based technique is of interest due to its low cost, high accuracy, and small size. In this talk the objective is to describe and present a novel way to determine in situ the ripening of fruits and how they can be applied in real time applications. This methodology has been applied to determine the quality of fruits like Durian, Banana, Mangosteen and the like.

 

A number of techniques exist for characterization of lossy dielectric objects at microwave frequencies. Many such techniques have been extensively developed, e.g. resonant and non-resonant methods. For the resonant method, the cavity perturbation technique is well suited for measuring low dielectric loss materials and the accuracy is limited only by the size of the cavity. For a non-resonant method, the transmission line technique needs an adequate thickness of the sample. An open-ended probe technique, which has been successfully commercialized, can measure over a wide frequency range with moderate accuracy, but the material sample must be sufficiently thick and the contact surface of the probe must be flat and free of air gaps.


In this methodology we propose to use a free space measurement technique used in RCS measurements and use the natural resonant frequency concepts to estimate the variation of the dielectric properties with time, and thereby relate to the physical characteristics of the fruit. What makes the problem challenging is that both the real and the imaginary parts of the dielectric constant for most frits is extremely high and even much greater than that of sea water! The variation of these electrical properties as a function of frequency will be described and how the singularity expansion method can be applied to estimate the variation of the natural resonant frequency of the various fruits as it ripens changing the sugar content with time will also be discussed.


In a free-space measurement technique, the amplitude and the phase of the returned probing signal are measured from a sample of interest which is placed between a transmitting and a receiving antenna. Thus, the measurement setup is quite complicated since one needs to measure both the magnitude and phase of the scattered signal. There have been attempts to simplify the measurement system. An interesting method is to omit the phase and measure only the reflection and the transmission coefficients instead. Subsequently, a coupled-dipole sensor using the magnitude of  and  has been developed.
This talk will provide an overview of the various measurement techniques and try to relate the electrical properties to the physical properties of the various fruits.

 

  

An Adhoc Wireless Communications Network to Monitor Fruits on Trees in a Rural Environment


A wireless sensor network plays an important role in various applications, e.g., surveillance, defense, environmental monitoring, rescue, etc., including agriculture. An example of interest is to apply this methodology for farm management and perform in-situ quality control of agricultural products.


For an effective design of a wireless communications system in a rural environment, measured channel characteristics are highly desirable. Much work has been conducted on characterizing propagation through foliage but very few of them are really applicable for characterizing a propagation channel under a tree canopy. Although the physical principles are not different from a conventional system characterization, but the details are significantly different. The channel model in an orchard and on a tree will be described including environmental effects. The obtained channel model enables the system designer install suitable antennas for wireless communications under a tree canopy.
Specifically, the use of a wireless sensor network for pre-harvesting control of fruits will be presented in this talk.

 

 

A Phased Array Consisting of Switched Beam Elements in Improving Channel Capacity


Due to a dramatic increase of users in any application, the channel capacity is always invariably insufficient. A number of techniques have been introduced to address this problem by reducing multipath fading, delay spread and co-channel interference. A smart antenna system; classified into diversity, switched-beam, and adaptive antennas are possible good candidates. However, a switched-beam antenna is interesting due to its simplicity and thus low cost.


A phased array of switched-beam elements (PASE) has been developed based on a circular array in which the elements are capable of beam switching. It has been applied for improving signal to interference ratio (SIR). Instead of using PIN diodes for beam switching in the elements, a probe switching methodology to the implementation simpler has been proposed.


This beam switching element has been further developed for dual band operation. To form a circular array of PASE, study on the mutual coupling has been conducted for appropriate feed design for the antennas. Along with the phased array concept the constant modulus algorithm (CMA) for fast convergence is proposed for further improving the rate of convergence. Recently, PASE has been proposed for angle of arrival (AOA) measurement and dual band PASE is introduced for dual band operation.


This talk describes the principle of PASE and illustrates some of its applications.

 


Prof. Yahia Antar
Department of Electrical and Computer Engineering
Royal Military College of Canada
PO Box 17000, Station Forces
Kingston, Ontario CANADA
K7K 7B4
antar-y@rmc.ca

 

Dr. Yahia Antar received the B.Sc. (Hons.) degree in 1966 from Alexandria University, and the M.Sc. and Ph.D. degrees from the University of Manitoba, in 1971 and 1975, respectively, all in electrical engineering.

In 1977, he was awarded a Government of Canada Visiting Fellowship at the Communications Research Centre in Ottawa where he worked with the Space Technology Directorate on communications antennas for satellite systems. In May 1979, he joined the Division of Electrical Engineering, National Research Council of Canada, Ottawa, where he worked on polarization radar applications in remote sensing of precipitation, radio wave propagation, electromagnetic scattering and radar cross section investigations. In November 1987, he joined the staff of the Department of Electrical and Computer Engineering at the Royal Military College of Canada in Kingston, where he has held the position of professor since 1990. He has authored or co-authored close to 200 journal papers, many chapters in books ,about 350 refereed conference papers, holds several patents, chaired several national and international conferences and given plenary talks at many conferences . He has supervised and co-supervised over 80 Ph.D. and M.Sc. theses at the Royal Military College and at Queen’s University, of which several have received the Governor General of Canada Gold Medal, the outstanding PhD thesis of the Division of Applied Science as well as many best paper awards in major international symposia. He served as the Chairman of the Canadian National Commission for Radio Science (CNC, URSI,1999-2008), Commission B National Chair (1993-1999),held adjunct appointment at the University of Manitoba, and, has a cross appointment at Queen's University in Kingston. He also serves, since November 2008, as Associate Director of the Defence and Security Research Institute (DSRI).

 

Dr. Antar is a Fellow of the IEEE (Institute of Electrical and Electronic Engineers), a Fellow of the Engineering Institute of Canada (FEIC), a Fellow of the Electromagnetic Academy, serves as an Associate Editor (Features) of the IEEE Antennas and Propagation Magazine, served as Associate Editor of the IEEE Transactions on Antennas and Propagation, IEEE AWPL, and was a member of the Editorial Board of the RFMiCAE Journal. He served on NSERC grants selection and strategic grants committees, Ontario Early Research Awards (ERA) panels, and on review panels for the National Science Foundation.

 

In May 2002, Dr. Antar was awarded a Tier 1 Canada Research Chair in Electromagnetic Engineering which has been renewed in 2009. In 2003 he was awarded the Royal Military College of Canada “Excellence in Research” Prize and in 2012 the Class of 1965 Teaching Excellence award. He was elected by the Council of the International Union of Radio Science (URSI) to the Board as Vice President in August 2008, and to the IEEE Antennas and Propagation Society Administration Committee in December 2009. On 31 January 2011, Dr Antar was appointed Member of the Canadian Defence Science Advisory Board (DSAB).

Dielectric Resonator Antenna for Wireless and Other Applications


Pioneering investigations with the dielectric resonator as a radiator date back to the work of Long and his associates in 1983.  Since then many groups of researchers all over the world have been active in this area of research and have made remarkable advances during the last two decades.  The main goals have been to explore efficient feeding techniques, methods to obtain wide and ultra wide impedance bandwidth, high gain, new geometrical shapes for improved features, etc.  Indeed from the very beginning of DRA research, it has been regarded as a variant of the planar radiator like a microstrip patch , but compared to microstrip it is more advantageous in many aspects and also there are some disadvantages too.  Some new efforts have also been made to integrate microstrip structures with a DRA to achieve better performances.  As has been demonstrated, DRAs offer a high degree of flexibility and versatility over a wide frequency range allowing the designer to suit many requirements.  Many new elements and arrays with attractive characteristics for wireless and other applications have been implemented and a description of some of these is included in the literature.

 

Even after many new developments and achievements, practical design, fabrication and implementation of these DRAs are still challenging in many cases.  In recent years, more focus has been given to enhance antenna bandwidth efficiency and gain which are more relevant to the requirement of modern wireless applications.  Many new techniques have been explored; most of them apply various composite and hybrid type structures.  Furthermore, due to the mature technology of microwave and millimetre wave integrated circuits, on-chip DRAs have recently received a great deal of attention because they can be more efficient, reduce the size, weight and cost of many transmit and receive systems.


This presentation will address the basic fundamentals of DRAs, most recent development and research directions.

 

 

New Considerations for Antenna Electromagnetic Near Fields


This presentation focuses on introducing a new fundamental approach to some electromagnetic phenomena with particular focus on antenna systems.  The theme chosen here is the near-field zone of electromagnetic radiation which is crucial and pertinent to the scientific understanding of how electromagnetic devices work and consequently is critical for product design and development.  Starting with the familiar radiation expressions obtained from Maxwell’s equations, we proceed to build a new formulation of radiation and interaction, coupling and energy transfer, all at a general level.  One of the main thrusts considered will be a look at possible future directions of research into new potentials for viewing and monitoring the structure of electromagnetic radiation.  In particular, we will discuss new paths towards a deeper understanding of electromagnetic radiation that go beyond the usual measures of impedance parameters and radiation pattern. A new perspective on the origin of radiation in the near field zone will be introduced.

 

These new theoretical development start from the classical Wilcox and Weyl expansions in electromagnetic theory, where they are deployed in a new fashion in order to provide insights into the nature of electromagnetic radiation and antenna systems in particular.  The conventional concepts of reactive and stored energies are revisited and formulated on a new basis that is general and comprehensive.  As an example, a distinction between various genera of energy processes in the near field zone is proposed and verified by careful exposition of the physical content of the electromagnetic field viewed here as a moving quantum of energy.  The theory leads naturally to new generalizations of the classical Poynting theorem in order to take into account the interaction between propagating and non-propagating modes, a topic that needs to be given more attention in both theoretical and applied electromagnetics.  The formulation links the spatial (Wilcox) and spectral (Weyl) perspectives by deriving a new hybrid expansion and suggests possible organic connections between the far and near fields.  Some of the applications of the near field theory involve an attempt to characterize and understand the phenomena of electromagnetic interactions and mutual coupling between various antenna/scatterer systems.  It is hoped that this comprehensive rigorous theory for the near fields would help in providing new understanding and new mechanisms for dealing with some important phenomena in applied electromagnetics.

A Class of Printed Leaky Wave Antennas


Leaky wave antennas form one type of traveling wave antennas in which an aperture is illuminated by the fields of a traveling wave.  Usually a leaky wave stems from a close guiding structure that supports traveling waves but has some means of continuous power leakage into the exterior region.  The illuminated aperture extends over several wavelengths and is limited by wave attenuation caused by power leakage.  In a typical leaky wave antenna structure, an incident mode travels inside a wave guiding structure with one of the sides allowing power leakage causing some perturbation to the propagating mode.  Therefore, assuming propagation in the z direction, the mode longitudinal wave number bzs in a completely closed waveguide will be slightly changed to, say bz, and there appears, in addition an attenuation factor az.  Therefore, a leaky mode is one having a complex wave number kz = bz – jaz, where bz is less than the free space wave number k0 rendering the leaky mode to be a fast wave.  A leaky mode will radiate in a direction q given by q = sin-1(bz/k0).  Since bz is a function of frequency, it follows that the radiation beam can be steered by frequency scanning between broadside and end fire.  The beamwidth depends on the attenuation rate az.  As az is reduced, the illuminated aperture extends over larger area resulting in higher directivity and lower beamwidth.

 

The basic properties of leaky wave antennas were founded in the pioneering work of Tamir and Oliner back in the early 1960s and later in the work of Jackson and Oliner.  Recently, the need for high gain microstrip antennas has revived interest in leaky waves resulting in a great number of papers on printed leaky wave antennas also by Jackson and others. In here we discuss leaky waves and their supporting structures.  We describe a leaky wave mathematically as a complex plane wave.  The leaky mode supporting structure is treated as a perturbation of a closed waveguide.  A planar antenna configuration with a partially reflecting screen will be studied in detail as an example of a leaky wave antenna structure. Another example of such a structure is a multilayered planar antenna with the capability of gain enhancement.  Analysis of these two structures reveals the main properties of leaky wave antennas and provides some physical insight into their nature.  In addition, we present practical designs of one-dimensional and two-dimensional leaky wave antennas that radiate fan-shaped beams and conical or pencil beams respectively, along with some planar feeding schemes.


2013-2015

 

Prof. Ari Sihvola
Aalto University, Department of Radio Science and Engineering
Box 13000, FIN-00076 Aalto
FINLAND
ari.sihvola@aalto.fi

Ari Sihvola was born in 1957, in Valkeala (Finland). He received the degrees of Diploma Engineer in 1981, Licentiate of Technology in 1984, and Doctor of Technology in 1987, all in Electrical Engineering, from the Helsinki University of Technology (TKK), Finland. Besides working for TKK and the Academy of Finland, he was visiting engineer in the Research Laboratory of Electronics of the Massachusetts Institute of Technology, Cambridge, in 1985–1986, and in 1990–1991, he worked as a visiting scientist at the Pennsylvania State University, State College. In 1996, he was visiting scientist at the Lund University, Sweden, and for the academic year 2000–2001 he was visiting professor at the Electromagnetics and Acoustics Laboratory of the Swiss Federal Institute of Technology, Lausanne. In the summer of 2008, he was visiting professor at the University of Paris XI, France. Ari Sihvola is professor of electromagnetics in Aalto University School of Electrical Engineering (Aalto University was created in 2010 as a merger of three universities: Helsinki University of Technology, Helsinki School of Economics, and the University of Art and Design). His scientific interests range from electromagnetic theory, complex media, materials modeling, remote sensing, and radar applications, into engineering education research and history engineering and technology. Ari Sihvola is Chairman of the Finnish National Committee of URSI (International Union of Radio Science), Vice Chairman of the Commission B (Fields and Waves) of the international URSI, and Fellow of IEEE. In 1990’s, he has served as Chairman of the IEEE AP–MTT Chapter for several years. He was awarded the five-year Finnish Academy Professor position in 2005–2010. He is also director of the Finnish Graduate School of Electronics, Telecommunications, and Automation (GETA). Author of several books and hundreds of publications, Ari has been active in organizing conferences and workshops, convening and chairing sessions, and serving in advisory, technical, and organizing committees for numerous national and international scientific symposia as member, secretary, or chairman. In TKK and Aalto University, Ari Sihvola has received several teaching awards, like the “Teacher of the Year” Prize in 1995 from the Student Union of TKK.

 


Characterization and Effective Description of Heterogeneous and Composite Electromagnetic Materials


In the analysis of electromagnetic fields interacting with material structures, the response of medium is condensed in dielectric and magnetic material parameters, like permittivity, conductivity, and permeability. In complicated and anisotropic media, these material parameters may need to be generalized from scalar quantities into matrices, or equivalently dyadics. The complicated response of materials is very often of structural origin, in other words the manner in which a heterogeneous mixture is formed determines its macroscopic electromagnetic material parameters. This lecture deals with the variety of ways how one is able to characterize and effectively describe the macroscopic dielectric and magnetic behavior of composite materials with given properties of the constituents and the geometrical microstructure. The rich history of homogenization of mixtures will be reviewed, including Clausius−Mossotti, Lorenz−Lorentz, Maxwell Garnett, Bruggeman, and other homogenization principles, and their ranges of applicability will be assessed. Mixing principles will be applied to mixtures that display very interesting properties that differ strongly from those of the constituent materials, like, for example, aqueous, strong-contrast, lossy, plasmonic, chiral, and bianisotropic mixtures.

 

Boundary Conditions and Extreme-Parameter Materials in Electromagnetics


In electromagnetics, the distinction between a boundary and an interface is fundamental. It is essential to emphasize the difference between these two concepts because very often in applied electromagnetics and in metamaterials studies, confusions exist. One often hears the question: “What is the material behind the surface on which a boundary condition is assumed?” The answer is, of course, that such a question is meaningless: nothing in the space on the other side of the boundary affects the fields in the domain of interest. On a boundary of a given spatial domain, electromagnetic fields have to be forced to satisfy a certain boundary condition in order to uniquely determine the field solutions. An interface problem is fundamentally different: the fields in the two domains have an interaction through tangential continuity conditions across the interface. The boundary–interface issue has a special significance in metamaterials studies where quite often the focus is on media with extreme constitutive parameters. Even if the boundary problem is different from the interface problem, they can be approximations or idealizations of each other. However, here it is important to keep clear what is the starting point and what is the approximation. Sometimes the interface problem is approximated by a boundary problem, which idealizes the situation and hence simplifies the analysis. The complementary procedure is a synthetic approach, where the boundary problem is primary and the question is how to construct and synthesize a real-world material structure that would best approximate the starting-point situation with the ideal boundary. In this lecture, I focus on this important distinction and show how well certain boundary conditions and complex surfaces can be simulated by material structures.

 

Philosophy of Metamaterials and Metasystems


Metamaterials have entered into the mainstream of electromagnetics, high-frequency engineering, and materials science research within a relatively short period. Even if the rapid progress in this field owes very much to earlier studies, it has managed to find a distinct profile and visibility within the first decade of the 21st century. Seminars, workshops, sessions, and even congresses dedicated to metamaterials are being organized, and the journal Metamaterials, published by Elsevier, runs already its sixth yearly volume (in 2012). Several books on the topic have appeared during the latest years. The potential for applications of metamaterials in the nanoscale, by manipulation of optical waves, has given rise to the field of metatronics. The prominence of metamaterials research wave is affecting the way electromagnetics problems and questions are approached even to the extent that one may talk about a metamaterials paradigm in research. The essential property in metamaterials is their unusual and desired qualities that appear due to their particular design and structure. These advantageous properties are not straightforward linear functions of the constituents from which the metamaterial is built up. A sample of metamaterial is more than a sum of its parts, analogously to the taste of ice-cream, which is not a direct sum of the flavors of ice and cream. Taking a more general perspective, we may observe that in the field of electromagnetic materials, there are several examples of media that fully deserve to be labeled metamaterials. Chiral (spatial-parity-breaking structures) materials, artificial magnetism, magnetoelectric materials, percolation processes, extremely anisotropic media, and other special media are complex enough to fall in the category of metamaterials. This lecture discusses fundamental issues associated with metamaterials, like possibilities to find a unique definition for them, the spatial scales and geometrical constellations for which one can talk meaningfully about metamaterials, and meta-type characterization of engineering structures and systems in general.

 


Mats Gustafsson
Department of Electrical and Information Technology
Lund University
Box 118
SE-221 00 Lund
Sweden
mats.gustafsson@eit.lth.se
http://www.eit.lth.se/staff/mats.gustafsson

 

Mats Gustafsson received the M.Sc. degree in Engineering Physics in 1994, the Ph.D. degree in Electromagnetic Theory in 2000, was appointed Docent in 2005, and Professor of Electromagnetic Theory 2011, all from Lund University, Sweden.

 

He co-founded the company Phase holographic imaging AB in 2004.  His research interests are in scattering and antenna theory and inverse scattering and imaging with applications in microwave tomography and digital holography. He has written over 60 peer reviewed journal papers and over 75 conference papers. 

 

Prof. Gustafsson received the best antenna poster prize at EuCAP 2007 and the IEEE Schelkunoff Transactions Prize Paper Award 2010.

 

Convex Optimization for Analysis of Small Antennas


Design of small antennas is challenging as the Q-factor, efficiency, and radiation resistance must be controlled simultaneously. In this presentation, it is shown that convex optimization together with closed form expressions of the stored electromagnetic energies provide a general method for analyzing many fundamental antenna problems. The solution to the convex optimization problem determines optimal currents, offers insight for antenna design, and presents performance bounds for antennas.

 

We present optimization formulations for the maximal gain Q-factor quotient, minimal Q for superdirectivity, and minimal Q for given far field. The effects of antennas embedded in metallic structures and effects of losses are also discussed. Results are shown for various antenna geometries and compared to state of the art designs. It is also shown that many antennas perform almost optimally. A tutorial description of a method of moment implementation together with a Matlab package for convex optimization to determine optimal current distributions on arbitrarily shaped antennas is also presented.

 

Sum Rules and Physical Bounds in Electromagnetics


Sum rules can be used to construct physical bounds on many types of physical systems.  The physical bounds answer questions like; what is the minimal temporal dispersion of passive metamaterials, how does the thickness influence the performance of absorbers and high-impedance surfaces, how does the inter-element coupling affect frequency selective surfaces, how does the bandwidth and directivity depend on the size of antennas, and what is the available bandwidth in extra-ordinary transmission of electromagnetic waves through sub-wavelength apertures. These types of identities and bounds are of great interest in many areas of physics and engineering. They also provide insight into the relationship between design parameters. The mathematical analysis is based on integral identities for Herglotz (or positive real) functions. These integral identities are referred to as sum rules and generalize the classical Kramers-Kronig dispersion relations to physical systems satisfying the underlying principles of linearity and passivity.

 

In the talk, we present the mathematical background based on time domain passive systems, Herglotz (or positive real) functions, and integral identities (sum rules) for passive systems. We analyze and present physical bounds for; broadband matching, radar absorbers, high-impedance surfaces, temporal dispersion of metamaterials, sub-wavelength scatterers, extraordinary transmission, and small antennas. We also compare the theoretical results with state of the art designs.

 

 

Near-field Diagnostics of Antennas and Radomes


Visualization of electromagnetic field and currents facilitates our understanding of the interaction between fields and devices. This is easily done in numerical simulations where the electromagnetic fields can be computed directly. It is much harder in most measurement situations where the fields cannot be measured directly and must instead be reconstructed from measurements of the fields outside the object or volume of interest. This reconstruction requires the solution of an inverse source problem. Reconstructions of field and current distributions are useful in applications such as non-destructive diagnostic of antennas and radomes and assessment of specific absorption ration (SAR) in the human body due to base station radiation.

 

In this presentation, we show how the field and current distribution can be reconstructed and visualized from near- and far-field measurement data. We illustrate how they can be used in antenna and radome diagnostics to, for example, identify faulty components. We discuss recent developments in inverse source problems to accurately reconstruct electromagnetic fields on a surface or volume from near- and far-field measurements. We review the theory for inverse source problems, non-uniqueness, and regularization. We present formulations based on equivalent currents using integral equations and integral representations for planar, spherical, body of revolution, and general geometries.

 

 

Prof. Ahmed Kishk
Department of Electrical and Computer Engineering
Concordia University
1455 De Maisonneuve Blvd. West, EV 005.139
Montreal, QC, Canada H3G 1M8
kishk@ece.concordia.ca

 

Dielectric Resonator Antennas

Abstract

The dielectric resonator antenna (DRA) is made from high dielectric constant materials and mounted on a ground plane or on a grounded dielectric substrate of lower permittivity.  DRAs have many attractive features such as small size, high radiation efficiency, wide bandwidth, and high power capability that make them attractive for radar applications and base stations.  An overview for the development of the dielectric resonator antennas will be given to provide understanding of dielectric resonator characteristics, operation, and design.  DRA arrays characteristics are provided with discussion on the mutual coupling level and the wide scanning capabilities. Finally, several examples of DRA for wideband, multifunction applications, and proposed new application of embedded DRA in energy harvesting environments.

 

Dielectric Resonator Antenna Arrays Excited by Waveguide Slots and Probes

Abstract

Excitation of dielectric resonator antennas (DRAs) using rectangular waveguide slots and probes is studied. A method of moments (MoM) procedure is used to analyze a single DRA element as a first step. For slot excitation, transverse, longitudinal and tilted slots are considered and prove to be a weak coupling mechanism to DRAs, thus can be used for large arrays. Probe excitation, however, exhibits the possibility of strong coupling to the DRA with the proper choice of the design parameters, and thus a wide matching bandwidth can be achieved. An equivalent circuit model for both excitation mechanisms is developed to facilitate the extension of the study from the single element to the array. A simple design procedure for the array is developed based on the circuit model and the array performance is studied. Results show that the developed analysis and design tools give accurate predictions of the element and array return loss and radiation patterns.

 

UWB Antennas for Wireless Communication and Detection Applications

Abstract

Ultra-wide band (UWB) wireless communication occupies a bandwidth from 3.1 to 10.6 GHz, referred to as UWB band, to achieve high data rate over a short distance. Two competing schemes, namely multiband orthogonal frequency division multiplexing (MB-OFDM) and direct sequence ultra wide band (DS-UWB), were proposed to make use of the allocated bandwidth. Ideally, a transmitting/receiving UWB antenna pair comprising a communication channel should operate as a band-pass filter covering the UWB band and have a flat magnitude response and a linear phase response with frequency. It requires an UWB antenna well matched, with frequency independent phase center, and linearly increasing gain with frequency over the entire UWB band.

An omnidirectional UWB antenna is especially attractive to wireless communications at either base station or terminal side. For an omnidirectional UWB antenna, besides the aforementioned three requirements, its radiation performances over the UWB band should also be independent of the azimuth angle. A good impedance matching over the UWB band is not difficult, and many types of antenna can achieve that. Frequency independent phase center is achievable for most antennas except for those with multi-resonant structure spatially separated. But, after the first three requirements are met, a wideband omnidirectional radiation is still challenging for UWB antenna design.  Omnidirectional UWB antennas with a non-planar conducting structure as well as DRA are presented for an UWB access point.

Another recently addressed problem is the interference problem with the WLAN bands.  To prevent interference problems due to existing nearby communication systems within an Ultra-wideband operating frequency, the significance of an efficient band notched design is increased.  Two novel antennas are presented.  One antenna is designed for one band-notch. The second antenna is designed for dual band-notches 

Several UWB antennas with unidirectional patterns are presented for detection applications.  Dielectric resonator is used to tremendously shrink an UWB antenna’s size to be used as a sensor for breast cancer detection and microwave imaging. Another 3D conducting self-grounded Bow-Tie sensor is presented. The application of such a DR UWB antenna for thro-wall radar detection is also investigated showing better performance as compared to the Vivaldi antenna.

EM Modeling of Artificial Magnetic Conductors
 
Abstract

 

The term soft and hard surfaces is recently used with surfaces based on the direction of propagation along the surface. Soft surfaces are long been used in horn antennas as transverse corrugations to improve the radiation characteristics.  A grounded dielectric slab loaded with transverse metallic strips can realize also soft surfaces.  Longitudinal corrugations or longitudinal strips can realize hard surfaces. Such surfaces have recently found some applications and relation with the electromagnetic band gap surfaces (EBG) and artificially magnetic conducting surfaces (AMC). The analysis of these surfaces using exact boundary conditions is tedious and sometimes is limited to certain geometrical constraint when periodicity has to be analyzed using Floquet modes.  Recently, simplified boundary conditions have been developed to analyze such surfaces. Such boundary conditions remove the geometrical restrictions and able the analysis of complex surfaces with different types. These asymptotic boundary conditions are used under the condition that the structure period is very small compared to the wavelength and ideally when the period approaches zero. Three types of asymptotic boundary conditions are considered.  The asymptotic strips boundary conditions (ASBC) to be used with strips loaded surfaces. The asymptotic corrugations boundary conditions (ACBC) to be used with corrugated surfaces. The third type can be used with strips or corrugations under the assumption of ideal soft or hard conditions.  The surfaces can be model as periodic surface of perfect electric conducting strip (PEC) attached to a perfect magnetic conducting strip (PMC).  This boundary condition is referred to as PEC/PMC surface.  Also, the classical model of surface impedance boundary condition can be used with some of these surfaces.

A review related to these boundary conditions will be given. We will show the implementation of these boundary conditions in method of moments (MoM) based on surface integral equations and the finite difference time domain method (FDTD).  The advantages of using the asymptotic boundary conditions will be illustrated. The relation between the soft surfaces and the electromagnetic band gap (EBG) surfaces will be discussed. We will present several examples of applications such as compact horn antennas with soft or hard surfaces, reduction of blockage from cylindrical objects and others applications.

A newly developed guiding structure will be presented, which is based on the properties of the AMC with low loss. Also, a demonstration of using AMC in packaging microwave circuits will be presented. 

 

Analysis and Design of Wideband Dielectric Resonator Antenna Arrays for Waveguide-Based Spatial Power Combining

Abstract

Dielectric resonator antennas (DRAs) have attractive features such as small size, high radiation efficiency, wide bandwidth, and high power capability. These advantages made them attractive for use in different applications. Probe-fed dielectric resonator antenna arrays in an oversized dielectric loaded waveguide with hard horn excitation are investigated for their use in waveguide-based spatial power combining systems. The horn excitation could be considered as a space fed network for the dielectric resonators. A design of thin walled hard waveguide and hard horns are presented to provide uniform field distribution to provide uniform excitations for the array inside the hard structure.  Design procedures for the special power combiner using the DRA are presented. The design starts from a single DRA inside a hard waveguide. A single dielectric resonator antenna element excited by a coaxial probe is analyzed first inside a hollow rectangular waveguide and a TEM waveguide to show the needs for the hard waveguide (TEM waveguide) to provide the uniform field distribution. Then, one-dimensional dielectric resonator antenna arrays are studied inside the H-plane sectoral hard horns. An entire spatial power combining system with a two-dimensional dielectric resonator antenna array is analyzed inside a hard pyramidal horn. The analysis of the entire system is based on the finite-difference time-domain method with region-by-region discretization and sub gridding schemes. All these designs are constructed by the student using very limited resources. Simulation results are compared with measurement results and show good agreement.

Another design of wideband dielectric resonators system is analyzed and tested as a special power combiner. Use of the special power combiner as a space feed for a radiating array will also be considered. As still open research area hints for possible future work will be provided.

 

Study of SIW Circuits Using an Efficient Hybrid Method

Abstract

As the substrate integrated waveguide (SIW) is constructed by emulating the solid side walls of the waveguide using two rows of metal posts, the thin wire approximations for these posts are found to be inadequate and the current variations around the posts must be considered. A numerical modeling for the posts as cylinders is found to be more realistic, but that presents a numerical burden in the analysis.  Therefore, a two-dimensional efficient full wave method is developed to analyze non radiating SIW circuits.  The method combines the cylindrical eigenfunction expansion and the method of moments to avoid geometrical descretization of the posts. The formulations for an SIW circuit printed on either homogeneous or inhomogeneous substrate are presented. With the ability to model inhomogeneous substrate, the cylindrical eigenfunction expansions are used to model the inhomogeneity. Therefore, circuits with metal and/or dielectric posts are analyzed. This facilitates designs of filters based on SIW structures are designed with metallic or dielectric resonators embedded inside the substrate.  The talk also covers the microstrip-to-SIW transition and the speed-up technique for the simulation of symmetrical SIW circuits. Different types of SIW circuits will be presented using the proposed method.

 

Wideband Dually Polarized Microstrip Air Patch Antennas and Dielectric Resonator Antennas

Abstract

For today’s communication, wide frequency band, low cross-polarization and high isolations are required for dually polarized antennas. In this presentation, several designs for air patches, Huygens’ source antenna, and dielectric resonator antennas are presented. Several excitation techniques are presented to achieve wideband width and high isolations. Bandwidths between 25-50% are achieved with isolation between 30-40dB.

 

Biography
Ahmed A. Kishk received the BS degree in Electronic and Communication Engineering from Cairo University, Cairo, Egypt, in 1977, and BSc. in Applied Mathematics from Ain-Shams University, Cairo, Egypt, in 1980.  In 1981, he joined the Department of Electrical Engineering, University of Manitoba, Winnipeg, Canada, where he obtained his M.Eng and PhD degrees in 1983 and 1986, respectively.  From 1977 to 1981, he was a research assistant and an instructor at the Faculty of Engineering, Cairo University.  From 1981 to 1985, he was a research assistant at the Department of Electrical Engineering, University of Manitoba.  From December 1985 to August 1986, he was a research associate fellow at the same department.  In 1986, he joined the Department of Electrical Engineering, University of Mississippi, as an Assistant Professor. He was on sabbatical leave at Chalmers University of Technology, Sweden during the 1994-1995and 2009-2010 academic years. He was a Professor at the University of Mississippi (1995-2011). He was the director of the Center of Applied Electromagnetic System Research (CAESR) during the period, 2010-2011. Currently he is a Professor at Concordia University, Montréal, Québec, Canada (since 2011) as Tier 1 Canada Research Chair in Advanced Antenna Systems. He was an Associate Editor of Antennas & Propagation Magazine from 1990 to 1993.  He is now an Editor of Antennas & Propagation Magazine.  He was a Co-editor of the special issue, “Advances in the Application of the Method of Moments to Electromagnetic Scattering Problems,” in the ACES Journal.  He was also an editor of the ACES Journal during 1997.  He was an Editor-in-Chief of the ACES Journal from 1998 to 2001. He was the chair of Physics and Engineering division of the Mississippi Academy of Science (2001-2002). He was a guest Editor of the special issue on artificial magnetic conductors, soft/hard surfaces, and other complex surfaces, on the IEEE Transactions on Antennas and Propagation, January 2005. He was a technical program committee member in several international conferences.

His research interest includes the areas of design of Dielectric resonator antennas, microstrip antennas, small antennas, microwave sensors, RFID antennas for readers and tags, Multi-function antennas, microwave circuits, EBG, artificial magnetic conductors, soft and hard surfaces, phased array antennas, and computer aided design for antennas. Design of millimeter frequency antennas; Feeds for parabolic reflectors. He has published over 220-refereed Journal articles and 380 conference papers.  He is a coauthor of four books and several book chapters and editor of one book. He offered several short courses in international conferences.

Dr. Kishk and his students are the recipient of many awards. Dr. Kishk received the 1995 and 2006 outstanding paper awards for papers published in the Applied Computational Electromagnetic Society Journal. He received the 1997 Outstanding Engineering Educator Award from Memphis section of the IEEE. He received the Outstanding Engineering Faculty Member of the Year on 1998 and 2009, Faculty research award for outstanding performance in research on 2001 and 2005. He received the Award of Distinguished Technical Communication for the entry of IEEE Antennas and Propagation Magazine, 2001.  He also received The Valued Contribution Award for outstanding Invited Presentation, “EM Modeling of Surfaces with STOP or GO Characteristics – Artificial Magnetic Conductors and Soft and Hard Surfaces” from the Applied Computational Electromagnetic Society. He received the Microwave Theory and Techniques Society Microwave Prize 2004.  Dr. Kishk is a Fellow of IEEE since 1998, Fellow of Electromagnetic Academy, and Fellow of the Applied Computational Electromagnetic Society (ACES).  He is a member of Antennas and Propagation Society, Microwave Theory and Techniques, Sigma Xi society, U.S. National Committee of International Union of Radio Science (URSI) Commission B, Phi Kappa Phi Society, Electromagnetic Compatibility, and Applied Computational Electromagnetics Society.