Ahmed A Kishk
Concordia University
Montreal, Canada

Speaker’s Biography: Ahmed A. Kishk received a BSc in Electronics and Communication Engineering from Cairo University, Cairo, Egypt, in 1977 and a BSc. in Applied Mathematics from Ain-Shams University, Cairo, Egypt, 1980. In 1981, he joined the Department of Electrical Engineering, University of Manitoba, Winnipeg, Canada, where he obtained his M. Eng. and Ph.D. degrees in 1983 and 1986. From 1977 to 1981, he was a research assistant and an instructor at the Faculty of Engineering at 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 in the same department. In 1986, he joined the Department of Electrical Engineering at the University of Mississippi as an assistant professor. He was on sabbatical leave at the Chalmers University of Technology, Sweden, during the 1994-1995 and 2009-2010 academic years. He was a Professor at the University of Mississippi (1995-2011). He was the Center for Applied Electromagnetic System Research (CAESR) director from 2010 to 2011. 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 Society Newsletters from 1990 to 1993. He was a distinguished lecturer for the Antennas and Propagation Society (2013-2015). He was an Editor of Antennas & Propagation Magazine (1993-2014). 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 in 1997. He was an Editor-in-Chief of the ACES Journal from 1998 to 2001. He was the chair of the 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 in the IEEE Transactions on Antennas and Propagation, January 2005. He was a co-guest editor for IEEE Antennas and Propagation and Wireless Letter on the special cluster on “5G/6G enabling antenna systems and associated testing technologies.” He was a technical program committee member for several international conferences. He was a member of the AP-S AdCom (2013-2015). He was the 2017 AP-S president.
Prof. Kishk's research interest is broad in Electromagnetic Applications. He has recently worked on millimeter-wave antennas for 5G/6G applications, Analog beamforming networks, Electromagnetic Bandgap, artificial magnetic conductors, soft and hard surfaces, phased array antennas, reflectors/transmitarray, and wearable antennas. In addition, he is a pioneer in Dielectric resonator antennas, microstrip antennas, small antennas, microwave sensors, RFID antennas for readers and tags, Multi-function antennas, microwave circuits, and Feeds for Parabolic reflectors. He has published over 465 refereed journal articles, 550 international conference papers, and 125 local and regional conference papers. He co-authored four books and 13 chapters and was the editor of eight books. He offered several short courses at international conferences. According to Google Scholar, his work was cited over 34930 with an H-index of 79 in the 9th edition of Research.com ranking of the best scientists in Electronics and Electrical Engineering; it is based on data consolidated from various sources, including OpenAlex and CrossRef. The bibliometric data for estimating the citation-based metrics were gathered on December 21, 2022. Prof. Kishk was ranked first at Concordia University, 23rd in Canada, and 401 worldwide. ScholarGPS has placed Dr Kishk in the top 0.05% of all scholars worldwide, with # 231 in Electrical Engineering, #4  in Antennas, # 5 in Dielectric, and #78 in Microwave.
Prof. Kishk and his students received several awards. He won 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 the Memphis section of the IEEE. He received the Outstanding Engineering Faculty Member of the Year in 1998 and the 2009 Faculty Research Award for Outstanding Research Performance in 2001 and 2005. He received the Award of Distinguished Technical Communication for IEEE Antennas and Propagation Magazine's entry, 2001. He also received The Valued Contribution Award for an 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 in 2004. He received the 2013 Chen-To Tai Distinguished Educator Award of the IEEE Antennas and Propagation Society. In recognition, “For contributions and continuous improvements to teaching and research to prepare students for future careers in antennas and microwave circuits, Kishk is a Fellow of IEEE since 1998, Fellow of Electromagnetic Academy, and a Fellow of the Applied Computational Electromagnetics Society (ACES). He is a member of the Antennas and Propagation Society, Microwave Theory and Techniques, Sigma Xi Society, and Senior member of the International Union of Radio Science, Commission B, Phi Kappa Phi, Electromagnetic Compatibility, and Applied Computational Electromagnetics Society.

Speech title: Compact Reflect/Tranmitarray Antennas

Abstract: A reflectarray (RA) antenna is a parasitic array of elements arranged periodically and spatially illuminated by a spherical wave generated by a feed located at a focal point away from the array. Conventionally, RA elements are arranged on a grounded planar surface. Thus, the focal point is virtual, chosen by the designer based on the feed characteristics. The RA antenna combines the characteristics of reflectors and array antennas. Thus, it can perform all the reflector and array antenna functions and overcome their disadvantages. 
Broadband planar reflectarrays are usually achieved by designing broadband elements with a large focal-to-diameter ratio (F/D). This requires a huge volume and relatively large and heavy feed. A small F/D should be used to reduce the feed size and volume. However, planar RA with a small focal-to-diameter ratio (F/D) suffers from limited bandwidth regardless of the element bandwidth. The primary factor hindering the bandwidth is increasing the planar-RA spatial path delay from the center to the edge, which introduces substantial phase variations that cannot adequately compensate for the RA elements away from the design frequency. A faceted RA was proposed, but the structure became more complicated, particularly for a small F/D. Here, a new simple RA design approach is proposed to enhance the bandwidth. Planar RA is cut to annular rings of sub-reflectarrays (sub-RAs), with the center sub-RA being circular. The sub-RAs are displaced to lower levels below the outer sub-RA and kept at the same position as the feed to reserve feed edge illumination. An overview of RAs and the parameters that control their performance is presented. The proposed structure, referred to as "Stepped RA," is presented by an example of circularly polarized RA. Cross-bowtie elements are used in the planar- and stepped RA with an aperture diameter 25.25λ. Element rotation is employed for phase compensation. The Stepped RA reduces the relative path delay as the ray moves toward the edge. A parametric study is performed, and a simple, compact Stepped RA is designed. The performance of the Stepped RA is compared to the Planar RA. The two RA configurations are fabricated and measured. The Stepped RA exhibits a matching bandwidth of 33.4 %, a 1-dB gain bandwidth of 23.2 %, a 1-dB axial ratio bandwidth of 33.4 %, and an aperture efficiency of 51 % (at 30 GHz). Based on the results, the stepped RA 1-dB gain bandwidth is improved by 13 % over the conventional planar RA. Other forms of compact RA are presented, such as the folded RA, which requires half of the focal length of the RA, and the wrapped RA constructed from textile material, both discussed in some detail.
In addition, transmitarry (TA) is where spherical waves impinge on a planar array of elements with two sides are discussed. The feed side is a receiving array of elements terminated by other elements on the other side to reradiate as a transmitting array. As in RA, the elements compensate for the phase errors and provide the required phases to reradiate to a specific direction or shape the beam.