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Distinguished Lecturers of the IEEE AP-Society

Mon, Mar 23    
  16:00 3D Propagation Modeling and Characteristics for High Speed Mobiles (C2C, C2X)
Werner Wiesbeck (University of Karlsruhe (TH), Germany)

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.
 
 
Tue, Mar 24    
  16:00 Electromagnetic Band Gap (EBG) Structures in Antenna Engineering: From Fundamentals to Recent Advances
Yahya Rahmat-Samii (University of California Los Angeles (UCLA), USA)

Periodic structures are abundant in nature, which have fascinated artists and scientists alike. When they interact with electromagnetic waves, exciting phenomena appear and amazing features result. In particular, characteristics such as frequency stop bands, pass bands, and band gaps could be identified. Reviewing the literature, one observes that various terminologies have been used depending on the domain of the applications. These applications are seen in filter designs, gratings, frequency selective surfaces (FSS), photonic crystals and photonic band-gaps (PBG), etc. We classify them under the broad terminology of “Electromagnetic Band Gap (EBG)” structures. EBG structures have provided promising paradigm for novel antenna designs. Due to the complexity of the EBG structures, it is usually difficult to characterize them through purely analytical methods. Instead, full wave simulators that are based on advanced numerical methods have been used in EBG analysis. Dispersion diagram, surface impedance, and reflection phase features are revealed for different EBG structures. These analysis tools have been integrated with modern optimization techniques such as genetic algorithms and particle swarm optimization to synthesis unique EBG structures. The applications of EBG structures in antenna designs have become a thrilling topic for antenna scientists and engineers. This is the central focus of this presentation by initially reviewing the fundamentals and then demonstrating recent advances. Utilizing several representative antenna examples it will be demonstrated that proper utilizations of EBG structures could enhance the performance of low profile antennas; however, considerable care must be exercised to fully appreciate their advantages and disadvantages
 
 
 
16:40 Antennas & RF Sensors: Changing the Way We Live (from mobile communications to electronic textiles and RFIDs)
John Volakis (Ohio State University, USA)

We already print more transistors than letters per year [IEEE Spectrum, 2008; www.ieee.org]. But to the average person, a more tangible technological impact has come from the proliferation of wireless devices that have truly changed our way of living, habits and business culture worldwide. Indeed, over the next decade, wireless devices and connectivity are likely to have transformational impact on our everyday life. Key to the wireless revolution is the implementation of multi-functionality and broadband reception at high data rates. This was a neglected area for several years as the industry was focusing on compact low noise circuits, and low bit error modulation techniques. However, as noted in a recent RF & Microwaves Magazine (www. mwrf.com) article, nearly 50% of a system-on-chip is occupied by the Radio Frequency (RF) front-end. Not surprising, the need for small antennas and RF front ends without compromising performance has emerged as a key driver in marketing and realizing next generation devices. The challenge in miniaturizing the RF front end was already highlighted by Harold Wheeler, one of the pioneers of optimal size antennas. He noted that “… [Electrical Engineers] embraced the new field of wireless and radio, which became a fertile field for electronics and later the computer age. But antennas and propagation will always retain their identity, being immune to miniaturization or digitization.” However, novel materials, either natural or in synthetic (metamaterials) form and a variety of synthesized anisotropic media are changing the status-quo. Also, materials such as modified polymers (friendly to copper) for silicon chip integration, high conductivity carbon nanofibers and nano-tubes, all coupled with 3D packaging are providing a new paradigm of integration attractive to the IC industry. Certainly, low loss magnetics, such as multiferroics or synthetic structures emulating magnetic structures, when and if realized, will provide one of the most transformational design impacts in the wireless industry. This presentation will provide an overview of the upcoming wireless applications and challenges. We will then discuss efforts towards the realization of novel materials (metamaterials and crystals, carbon nano-tubes, carbon nano-fibers and body worn devices, printing on polymers, multiferroics, etc) for RF miniaturization, including antennas that reach the optimum size limits.
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17:20 Microwave Antennas for Medical Applications
Koichi Ito (Chiba University, Japan)

In recent years, various types of medical applications of antennas have widely been investigated and reported. Typical recent applications are: (1) Information transmission: - RFID (Radio Frequency Identification) / Wearable or Implantable monitor - Wireless telemedicine / Mobile health system (2) Diagnosis: - MRI (Magnetic Resonance Imaging) / fMRI - Microwave CT (Computed Tomography) / Radiometry (3) Treatment: - Thermal therapy (Hyperthermia, Coagulation, etc) - Microwave knife In this presentation, three different types of antennas which have been studied in our laboratory are introduced. Firstly, a pretty small antenna for an implantable monitoring system is presented. 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.
 Wed, Mar 25    
  16:00 Reconfigurable Multifunctional Antennas
Christos Christodoulou (University of New Mexico, USA)

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 a 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 or PIN switches, or rotating feeds 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
  16:40 Cross-Layer Design of Smart Antenna Systems
Nicholas Buris (Motorola, Inc., USA)

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). 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.
  17:20 Higher Order Modelling for Computational Electromagnetics
Roberto Graglia (Politecnico di Torino, Italy)

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.
Thu, March 26    
  16:00 Miniaturization of Ultra-Wideband Antennas
Zhi Ning Chen (Institute for Infocomm Research, Singapore)

Ultra-wideband (UWB) has become the promising wireless technology in commercial applications such as the next generation of short-range high data rate wireless communications, high resolution imaging, and high accuracy radar. The antenna design becomes one of key factors in UWB wireless systems due to the extremely wide operating bandwidth. This presentation starts with the brief introduction of design challenges of UWB antennas. An outlined of special design considerations are presented from a systems point of view, followed by some state-of-the-art solutions which are shown with technical details from an engineering insight. Then, the miniaturization technology of UWB antennas is addressed. The planar designs are highlighted due to their unique merits and wide adoption in practical applications. Firstly, the ground plane dependence of the antenna performance, one of the most challenging issues in small antenna design is addressed. By using a newly developed technique, the dependence of small antenna performance on system ground plane has been alleviated. A design example is used to elaborate the mechanism of the method. Based on this concept, the antenna with further reduced size is designed to fit the size of wireless USB dongle for high data-rate applications. Furthermore, an innovative compact diversity UWB antenna is studied to show the advantage of ground-independence of small antenna in diversity applications. Lastly, a UWB antenna integrated with bandpass filter is proposed to reduce the overall size of devices by using the concept of co-design. In the end of the talk, the trend of UWB antenna R&D is offered according to application and market demands.
 
  16:40 Negative-Refraction Metamataterials and Their Applications
George Eleftheriades (University of Toronto, Canada)

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.
  17:20 THz Technology for Space and Terrestrial Applications
Peter de Maagt (European Space Agency, The Netherlands)

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.