Prof. Yahia Antar
Department of Electrical and Computer Engineering
Royal Military College of Canada
PO Box 17000, Station Forces
Kingston, Ontario CANADA
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.