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
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
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.
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.
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:
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/m^{2}. 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/m^{2}, but
rather is 121 or 81 W/m^{2}, 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 2^{63}
9.2 million Terabytes directly, which corresponds to the solution
of a 10^{9} X 10^{9} matrix in single precision
or a 0.76*10^{9} X 0.76*10^{9} 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
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 Awardsin 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 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 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 ofArtificial 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.