The IEEE AP-S Distinguished
Lecturer Program provides AP-S chapters in
the
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 local AP Chapter
Chairs for
the selection of appropriate topics and/or nominating Lecturers in the
future.
The list of all Distinguished Lecturers is available at the IEEE
website
relating to the Distinguished Lecturer Program, in addition to the AP-S
Magazine.
We welcome three new lecturers
for 2008-2010, namely,
Dr.-Ing.
Marta Martínez-Vázquez,
IMST,
The Chair of the Distinguished Lecturer Program is
J(Yiannis) C
Head of Electronic and Electrical Engineering Department
Professor of Wireless Communications
Loughborough University
Loughborough
Leicestershire, LE113TU
email: J.C.
Dr. Nicholas E. Buris
Motorola Labs
e-mail: nick.buris@motorola.com
Nick Buris received the diploma of
Electrical and Mechanical
Engineering in 1982 from the National Technical University of Athens,
Greece
and the Ph.D. in Electrical Engineering from the
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 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.
Institute for Infocomm Research
#02-21/25
chenzn@i2r.a-star.edu.sg
and znchen@ieee.org
Zhi Ning Chen received his BEng (1985), MEng
(1988), PhD (1993) and DoE (2003) degrees all in Electrical Engineering
from
Dr
Chen has organized many international technical events as general
chairs, technical program committee chairs and key members of
organizing
committees. He is the key founder of International Workshop on Antenna
Technology (iWAT).
Dr Chen has published more
than 210 journal and conference papers. He has authored and edited
books
entitled “Broadband Planar Antennas”, “UWB Wireless
Communication” and “Antennas for Portable Devices” all
published by John Wiley & Sons. He also contributed to the books of
“UWB Antennas and Propagation for Communications, Radar, and
Imaging” published by John Wiley & Sons as well as “Antenna
Engineering Handbook” published by McGraw Hill. He is holding more than
20 granted and filed patents. He has licensed his antenna designs to
industry
with deals. His current research interest includes applied electromagnetics,
antennas for UWB, MIMO, WLAN, WiMAX (WiBro), WBAN, and bio-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
Design
Considerations of Antennas for MIMO Systems
-Antenna
Engineering Perspectives
Christos G.
Christodoulou
ECE Department, Room 330
MSC01 1100
1 University of
Christos G. Christodoulou received his Ph.D. degree in
Electrical
Engineering from
Reconfigurable Multifunctional
Antennas
The requirements for increased
functionality, such as direction finding,
radar, control and command, within a confined volume, place a greater
burden in
today’s transmitting and receiving systems. A solution to this problem
is
the re-configurable antenna. Antennas that can be used for multiple purposes, that function over several frequency
bands and
that can be integrated on a package for mass-production are the
ultimate goals
of commercial and defense
investigators.
Furthermore, applications of such systems in personal and satellite
communications impose the requirement for elements miniaturized in size
and
weight.
Key-elements to obtain reconfigurability in
many RF circuits are the Radio-Frequency MicroElectroMechanical
Systems (RF-MEMS). Even though RF-MEMS have been used in the past to
reconfigure filters, phase-shifters, capacitors and inductors, their
integration in an antenna system has been limited as it faces a
plethora of
issues that need to be resolved. The absence of reconfigurable RF-MEMS
antenna
system and the recent advances in fractal - and especially Sierpinski
gasket- antennas combined with the availability of series cantilever
RF-MEMS
switches, sparked the pioneering idea to design a multiple-frequency
antenna
that will radiate on-demand the same radiation pattern at various
frequencies.
Such a system was designed and successfully implemented, as the first
functional, fully integrated RF-MEMS reconfigurable self-similar
antenna.
In this talk, several
reconfigurable antennas are presented and
discussed. The antennas to be presented cover a wide range of designs
such as
fractal antennas, triangular antennas, dipoles and monopoles with
variable
sleeves. All these antennas make use of MEMS switches, to make them
reconfigurable. Some of the challenges that the designer has to face in
biasing
and integrating these switches with the antenna has are also presented
and
discussed.
Using Support Vector Machines
in Electromagnetics
Since the 1990s there has been a
significant activity in the theoretical
development and applications of Support Vector Machines (SVMs).
The theory of SVMs is based on the
cross-pollination
of optimization theory, statistical learning, kernel theory and algorithmics. So far, machine learning has
largely been
devoted to solving problems relating to data mining, text
categorization, and
pattern/facial recognition but not so much in the field of electromagnetics.
Recently, however, popular binary machine learning algorithms,
including
support vector machines (SVM), have successfully been applied to
wireless
communication problems, notably spread spectrum receiver design and
channel
equalization. The high-speed capabilities and "learning" abilities of
support vectors can also be applied to solving complex optimization
problems in
electromagnetics in the areas of radar,
remote
sensing, microwaves, and antennas.
The aim of this talk is to
introduce the subject of support vector
machines in its linear and non linear form, both as regressors
and as classifiers and to show how it can be applied to several
problems in electromagnetics. The
intricacies and difficulties
associated with applying SVMs to complex
problems
will be discussed and it will be shown how to generate training and
testing
data that can be used with SVMs. Several
examples
that cover applications such as automatic target recognition in radar,
remote
sensing, beamforming, angle of arrival
estimation,
and microwaves will be presented and discussed.
George V. Eleftheriades
Department of Electrical and
Canada
George V. Eleftheriades earned his Ph.D.
and M.S.E.E.
degrees in Electrical Engineering from the University of
Michigan,
Dr. Eleftheriades received the Ontario
Premier's
Research Excellence Award and the Gordon Slemon
Award
from the
His present research interests lie in the areas of
negative-refractive-index metamaterials,
antennas and components for wireless
communications, novel antenna beam-steering techniques, low-loss
Silicon micromachined components,
sub-mm-wave radiometric
receivers, and electromagnetic design for high-speed digital circuits.
Negative-Refraction
Metamataterials and Their Applications
Recently there
has been renewed interest in man-made materials with electromagnetic
properties
that cannot be found in nature. Therefore these materials are referred
to as
“metamaterials” (“meta” means
“beyond” in Greek). This lecture addresses metamaterials
that can support negative refraction of electromagnetic waves. For
example, the
feasibility of media that simultaneously exhibit negative permittivity
and
negative permeability, hence a negative refractive index, has been
known since the
sixties. However it is only recently that people discovered how to
make
them. In such negative-refractive-index (NRI) or “left-handed” metamaterials, waves can be thought of as
propagating
backwards instead of forwards. When interfaced with conventional
dielectric
materials, incident waves become focused on a point instead of
diverging
outwards, thus suggesting the implementation of lenses with flat
surfaces.
In this lecture it will be demonstrated that NRI metamaterials
can be synthesized using planar networks of loaded transmission lines.
The
resulting metamaterials can be easily
constructed
using embedded capacitors and inductors. Since no resonators are
explicitly involved, they offer wide operating bandwidths. Based on
this
approach, microwave NRI metamaterial
lenses that can
resolve details beyond the classical diffraction limit will be
presented.
Alternative transmission-line metamaterials
that
support negative wave refraction will also be described. Moreover, a
number of
useful antenna and microwave devices, enabled by such
negative-refraction metamaterials will be
demonstrated. These enabling
materials and devices can find applications in diverse areas such as
wireless
communications, defence, and medical imaging.
Imaging Beyond The Diffraction Limit With
Negative-Refractive-Index Lenses
Classical
electrodynamics imposes a resolution limit when imaging with
conventional
lenses. This limit, called the “diffraction limit”, stems in
its ultimate form from the finite size of the wavelength of any
electromagnetic
monochromatic wave. Even when the aperture size of a lens is infinite,
the
maximum transverse wavenumber, kx,
that can contribute to the formation of the image is limited to
propagating
waves, i.e. kx <= k,
thus
determining the minimum resolvable detail to be on the order of one
wavelength, i.e. ~ 2/k =. Recently it
has been proposed that a lens made out of a slab of “left-handed”
or “negative-refractive-index” (NRI) material could overcome this
limitation by restoring not only the propagating waves kx
<= k emanating from the object, but also the evanescent waves
kx > k.
In this lecture, first the general electromagnetic properties of
NRI
media will be presented. This will be followed by an analysis of the
dispersion
characteristics of periodic transmission-line (TL) NRI media using a Floquet-Bloch analysis. Subsequently, the
imaging
properties of TL-NRI lenses will be examined through microwave
simulations, as
well as by means of the analytic derivation of their periodic Green’s
functions. The practical resolution limitations of such TL-NRI lenses
arising
from material losses, mismatches and the finite size of their unit
cells will
be revealed. Supporting experimental results for imaging beyond the
diffraction
limit will also be presented and related to theory.
Koichi Ito
Department of Medical System Engineering
Graduate School of Engineering
Chiba University
1-33 Yayoi-cho, Inage-ku,
Chiba-shi, 263-8522
Japan
ito.koichi@faculty.chiba-u.jp or k-ito@ieee.org
Koichi Ito received the B.S. and M.S. degrees from Chiba University,
Chiba,
Japan, in 1974 and 1976, respectively, and the D.E. degree from the 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
Dr. Ito is a
Fellow of the IEEE, a member of the American
Association for the Advancement of Science,
the
Institute of Electronics, Information and Communication Engineers
(IEICE) of
Japan, the Institute of Image Information and Television
Engineers of
Japan (ITE) and the Japanese Society for
Thermal
Medicine (formerly, Japanese Society of Hyperthermic
Oncology). He served as Chair of the Technical Group on Radio and
Optical
Transmissions, ITE from 1997 to 2001 and Chair of the Technical Group
on Human
Phantoms for Electromagnetics, IEICE from
1998 to
2006. He also served as Chair of the IEEE AP-S Japan Chapter from
2001 to
2002 and TPC Co-Chair of the 2006 IEEE International Workshop on
Antenna
Technology (iWAT2006). He currently serves as General Chair of
iWAT2008
to be held in
Microwave
Antennas for Medical Applications
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. An H-shaped cavity slot antenna is a
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 the 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.
Phantoms for
Evaluation of Interactions Between Antennas
and the
Human Body
In this presentation,
firstly, various types of numerical phantoms or models which are used
for
theoretical analysis and computational simulation are introduced.
Canonical phantoms such as sphere or cube have been mainly used for EM dosimetry inside the human head. In order
to estimate
the performance of the antenna close to the human body in the actual
situation
or SAR (Specific Absorption Rate) distribution inside the human body,
it is
sometimes necessary to use realistic numerical phantoms which are
composed of
many small voxels. On the contrary,
tissue-equivalent liquid, jelly, or solid phantoms are usually used for
experimental
evaluation. Then some different experimental phantoms are
introduced and
compared. There are two typical ways to evaluate SAR
distributions by
using experimental phantoms: the “electric-field method” with a
liquid phantom and the “thermographic
method”
with a solid phantom. Finally, this presentation introduces some
examples
of "new" solid phantoms including a UWB phantom and a torso phantom
which are used for the study on body-centric wireless communications.
Peter de Maagt
Antenna
and Submillimetre Wave Section
Electormagnetics & Space Environments
Division
European Space Agency
NL 2200 AG Noordwijk
The
peter.de.maagt@esa.int
Peter de Maagt was born in Pauluspolder,
The Netherlands, in 1964. He received the M.Sc. and Ph.D. degrees from
Eindhoven University of Technology,
Terahertz Technology for Space
and Earth Applications
The terahertz (THz) part of the
electromagnetic spectrum falls between
the lower frequency millimetre wave region
and, at
higher frequencies, the far-infrared region. The frequency range
extends from
0.1 THz to 10 THz, where both these limits are rather loose. As the THz
region
separates the more established domains of microwaves and optics, a
typical THz
technique will incorporate aspects of both realms, and may even draw on
the
best of both. The two bounding parts of the spectrum also yield
distinct sets
of methods of generating and detecting THz waves. These approaches can
thus be
categorised as having either microwave or optical/photonic origins. As
a result
of breakthroughs in technology, the THz region is finally finding
applications
outside its traditional heartlands of remote sensing and radio
astronomy.
Extensive research has identified many attractive uses and has paved
the
technological path towards flexible and accessible THz systems.
Examples of
novel applications include medical and dental imaging, gene theory,
communications and detecting the DNA sequence of virus and bacteria.
The
presentation will discuss the range of THz applications and will
present the
components and systems that are utilised for the frequency region.
Electromagnetic Bandgap Materials
Electromagnetic Bandgap Materials are
artificially engineered materials exhibiting novel properties. Since
their
discovery and first demonstration in the late 1980's, interest in EBGs has grown explosively. The potential takeup of these structures in Communications and
Sensing
Systems is primarily due to the control of the frequencies and wavenumbers of propagating and non-propagating
electromagnetic waves to an extent that was not previously possible.
Much
effort is now being concentrated on the design and manufacture of these
different classes of EBG-based components. This presentation will
highlight
application areas of EBG technology at microwave and (sub) millimetre
wave. It
sets out with a brief introduction of the concepts. It then discusses
some
generic configurations and resulting practical applications. Examples
of FSS,
EBG and AMC generic technology in the microwave region include: patch
antennas,
cavity antennas, parabolic antennas, metallo-dielectric
antennas, waveguides, filters and tunable
structures.
Examples of applications are array antennas, high precision GPS, mobile
telephony, wearable antennas and diplexing
antennas.
In the submillimetre wave region a 500 GHz
dipole
configuration is shown and some components.
Marta Martínez-Vázquez
Dr.-Ing. Marta Martínez Vázquez
Department of Antennas & EM Modelling
IMST GmbH
Carl-Friedrich-Gauß Str. 2
D-47475 Kamp-Lintfort
Germany
martinez@imst.de
Marta
Martínez-Vázquez was
born in
An overview of European
cooperation on antenna research
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
-
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
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 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.
Prof. Yahya
Rahmat-Samii
Electrical
rahmat@ee.ucla.edu,
Yahya Rahmat-Sami is a Distinguished
Professor of Electrical Engineering at the
The Marvels of Electromagnetic
Band Gap
(EBG) Structures
Periodic structures are abundant
in nature and they have fascinated
artistes and scientists alike. When these structures interact with the
electromagnetic waves amazing features result with many applications in
filter
designs, gratings, frequency selective surfaces (FSS), photonic
crystals/band-gaps (PBG), etc. Recently a unified classification of
various
nomenclatures under the broad terminology of “Electromagnetic Band
Gap
(EBG)” has been adopted. Ideally EBG structures are 3-D periodic
objects that prevent or assist the propagation of the electromagnetic
waves in
a specified band of frequency for allangles
and for all polarization states. However, in practice, it is
almost
impossible to construct such a complete band-gap structure and
frequently
partial band-gaps are achieved. FSS terminology has been used in the
microwave
community while PBG terminology has been applied in the optical
community. To
characterize some of the unique features of EBG structures, the
Spectral FDTD
technique with Periodic Boundary Condition/Perfectly Matched Layer
(PBC/PML)
has been successfully employed. The inherent broadband analysis of the
Spectral
FDTD approach provides an ideal capability when the structure is
characterized
to demonstrate its frequency and angular responses. Some unique
features of EBG
structures are demonstrated for microwave, antenna and optical
applications.
Results of simulations, prototyping and measurements will be presented
for
representative low profile antennas, array antennas and high Q
cavities. Future
prospects of EBG’s in electromagnetic
engineering designs will be addressed.
Personal Communication Antennas
including
Human Interactions: Handheld, Wearable and Implanted Devices
The introduction of personal
communications technology has resulted in a
widespread awareness of the critical role wireless services play in
today’s communications-centered
marketplace.
Antennas play paramount roles in an optimal design of the handheld,
wearable
and implantable devices used in these services. Clearly in designing
these
antennas the electromagnetic interaction among the antenna, devices and
the
human is a key factor to be considered. Additionally, diverse
requirements for
the various applications necessitate an in-depth evaluation of various
antenna
configurations including the effects of multi-path fading, human body
absorption, etc. In this presentation the following topics will be
addresses:
(a) The age of personal communications, (b) Modern electromagnetic
numerical
techniques for antenna performance evaluations, (c) Various popular
antenna
designs, such as, monopole, inverted F, reconfigurable patches, etc,
(d) Human
interactions with handheld devices, (e) wearable antennas and implanted
antennas, (f) Antenna diversity techniques to combat multipath,
(f) SAR characteristics for adults and children, and (g) future trends
in
personal communication antenna developments. Practical design and
safety issues
will be summarized based on our advanced computational methodology
utilizing
the real life model of a human body. Representative results will be
shown for
input impedance, bandwidth performance, patterns, polarization, gain,
absorbed
power, etc.
Genetic Algorithms (GA) and
Particle Swarm
Optimization (PSO) in Engineering Electromagnetics
Engineers are constantly
challenged with the temptation to search for
optimum solutions for complex system designs. The ever increasing
advances in
computational power have fueled this
temptation. The
well-known brute force design methodologies are systematically being
replaced
by the state-of-the-art Evolutionary Optimization (EO) techniques. EO
techniques have been successfully applied to problems in fields ranging
from
engineering to economics and artificial intelligence. Among various EO
techniques, Genetic Algorithms (GA) and Particle Swarm Optimization
(PSO) have
attracted considerable attention. GA utilizes an
optimization
methodology which allows a global search of the cost surface via the
mechanism
of the statistical random processes dictated by the Darwinian
evolutionary
concept. PSO is a robust stochastic evolutionary computation technique
based on
the movement and intelligence of swarms looking for the most fertile
feeding
location. This presentation will focus on: (a) an
engineering
introduction to GA and PSO, (b) demonstration of potential
applications
of GAs and PSO’s
to a
variety of electromagnetic engineering designs including communication
antennas, satellite antennas, radar absorbing materials for RCS
applications,
array antennas, and design of electromagnetic bandgap
(EBG) structures, and (c) assessment of the advantages and the
limitations of the techniques.
John L. Volakis
ElectroScience Laboratory
Dept. of Electrical and Computer Engineering
The Ohio State University
volakis@ece.osu.edu
John L. Volakis was born in
Metamaterials for
Miniaturization of Narrowband and Ultra-Wideband Antennas
It is well-recognized that
materials design holds promise in developing
novel antennas that are much smaller and allow greater
multi-functionality than
ever before. Such needs stem from the unprecedented growth of wireless
communications and related research that is highly fueled
by growth in commercial and defense
multi-band and
high bandwidth future communication systems. This presentation will
discuss how
modified materials, inductive/capacitive lumped loads and low loss
magnetic
materials/crystals (metamaterials) are
impacting
antenna design with the goal of overcoming miniaturization challenges
(viz.
bandwidth and gain reduction, multi-functionality etc.). Dielectric
design and
texturing has, for example, led to significant size reduction and
higher
bandwidth for low frequency antennas. Also, recent magnetic photonic
crystals (MPCs) and non magnetic versions
of these crystals hold a
promise for antenna/array miniaturization. Formal design methods
incorporating
local, global or hybrid optimizers for antenna and their radio frequency(RF) applications will play a critical
role in
materials design. Practical realizations of these new materials are
poised to
challenge computational and design methods for a variety of RF
applications.
Miniature Antennas & Arrays
Embedded
within Magnetic Photonic
Engineered materials, such as
new material composites, electromagnetic bandgap
and periodic structures have had strong interest in
recent years due to their extraordinary and unique electromagnetic behavior. Recently, a new class of magnetic
photonic
crystals (MPCs) and Double Band Edge (DBE)
that
display spectral nonreciprocity were
introduced.
Studies of these crystals demonstrated that MPCs
exhibit the interesting phenomena of (a) drastic incoming wave slow
down and
(b) significant amplitude growth while (c) maintaining a minimal
reflection at
the interface with free space . These
phenomena are
associated with the diverging frozen modes that occur around the
stationary
inflection points within the band diagram. Taking advantage of the
frozen mode
phenomena, we demonstrate that antenna elements embedded within the MPC
and DBE
structures allow for supergain effects
that can lead
to novel miniature array configurations configurations.
We will demonstrate these effects computationally using realistic
materials,
discuss loss issues, and gain sensitivity to the crystal thickness.
Also, as
part of the presentation, we will present an introduction to bandgap and bandedge
structures
and demonstrate the differences in the phenomena associated with the
MPC and
DBE crystals.
Hybrid Frequency Domain Methods
for Electromagnetics: From Analysis to
Design
The decade of the nineties is
highlighted with truly remarkable progress
in our ability to carry out simulations, not only for large scale
problems, but
also in terms of hybridization and integration of passive and active RF
circuits for a variety of applications. These developments have allowed
for
broadband antenna design, simulations of large multilayered and
multifunctional
antennas with embedded frequency selective surfaces (FSS), metamaterial
substrate designs, MEMS analysis and design, large finite arrays and
full scale
aircraft scattering analysis using first principle methods,
electromagnetic
coupling and interference of systems involving passive and active
components,
magnetic resonance imaging (MRI) simulations, indoor propagation and
evaluation
of wireless systems, etc. What is probably so remarkable is that a
decade ago
(early 90s), we had just started looking at three-dimensional
applications and
the development of practical simulation tools was seemingly far away.
Today, we
have access to robust and fast three dimensional algorithms for modeling composite materials and have also
demonstrated
that simulations of practical vehicles or large finite antenna arrays
and
possibly RF integrated systems can be carried out on a desktop PC. In
addition,
we have delved into topology optimization/design. The latter holds
promise for
novel antenna and microwave circuit design, RF filters and RFICs
for mixed signal applications, and others. This presentation
will
provide an overview of frequency domain developments, with particular
focus on
hybrid formulations and fast methods and their integration with formal
design
methodologies for antenna applications.
Werner Wiesbeck
Prof. Dr.-Ing.
Werner Wiesbeck
Inst. für Höchstfrequenztechnik
und Elektronik
Universität Karlsruhe (TH)
Kaiserstr. 12
76131
e.mail: 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
3D Propagation Modeling and Characteristics for High Speed
Mobiles
In existing
wireless telecommunication systems a user can choose either a high data
rate or
a high mobility. For various applications it would be desirable to have
both at
the same time: the freedom to move with a very high velocity without
loosing
the high data rate. Systems based on Orthogonal Frequency Division
Multiplexing
(OFDM) seem to be suitable to satisfy these conditions. However, the
high-speed
aspect has to be considered more closely. High-speed links between
receivers
and transmitters cause varying Doppler, delay and angular spread, which
may
result in inter-carrier in-terference (ICI) and inter-symbol interference (ISI).
ICI and
ISI are both a challenge and a limiting factor for a wireless
communication system.
Applications for high-speed mobile stations are for example on planes,
fast
cars, high-speed trains and so on. Several scenarios are chosen for the
simulations and partly verified by measurements. For cars these are
urban and a high way scenarios, for trains
high speed tracks with
buildings or forest environment are chosen. 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. The propagation channels are characterized by delay spread,
Doppler
spread and angular spread for different situations. These statistical
parameters are compared to measurements. Dynamic simulations will
be
illustrated by movies. The traffic scenarios are real world with
multiple
lanes, line of sight and non line of sight.
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 commu-nications
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 especially at the air interface, the antenna,
quite surprising behaviors.
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 an-tennas will be demonstrated by movies with a
pulse
excitation.
(modified:
28-July-2008)