Keynote Speaker 1
Metasurfaces for Energy Harvesting and Far-Field Wireless Power Transfer
Omar M. Ramahi
Electrical and Computer Engineering, University of Waterloo, Waterloo, ON, Canada
Far-field wireless power transfer (WPT) has been reconsidered in recent years as practical means to transfer power from outer space where satellites collect solar power with high efficiency using photovoltaic technology and then convert the power to microwaves for beaming to antenna farms at specific locations on earth. Conventional antennas have been the traditional microwaves transducers used for WPT applications. Almost all antennas that were considered for WPT applications were designed in the first place for communication applications where traditional antenna parameters such as gain, directivity and efficiency were considered the most critical. For WPT applications, however, the primary concern is to collect as much power as possible per footprint, based on specific polarization and incident angle.
Metamaterials are made of a three-dimensional ensemble of electrically-small resonators. Metasurfaces are considered as a two-dimensional version of metamaterials. The interesting and desired properties of metamaterials or metasurfaces are achieved when all elements of the ensemble operate at their resonance frequency (for simplicity, we assume all elements are identical). The resonance of each particle of a metamaterial or metasurface is fundamentally indicative of its ability to store energy. Metamaterials, therefore, can be effective energy collectors. This does not come as a surprise since metamaterials have been shown to be highly effective absorbers. However, in the case of absorption, the absorbed energy is mostly dissipated in the dielectric host. For the effective use of metamaterial as energy harvesters or collectors, not only the energy absorption is of high importance but also channeling the absorbed energy into energy collection channels is critical.
In this presentation, I will demonstrate that metasurfaces can indeed be effective electromagnetic energy harvesters and can provide energy harvesting efficiency appreciably higher than what classical antennas can achieve. The effectiveness of the metasurface for energy harvesting arises from the close proximity between the electrically-small resonators that constitute the metasurface. While the spacing between electrically-small resonators is critical to achieve homogenization for classical metamaterial applications, in energy harvesting, the spacing between elements allow for careful input impedance tuning of all elements, thus enabling highly efficient energy transduction. In this talk, I will present metasurfaces composed of different types of resonators including split-ring resonators, electric-inductive-capacitive resonators, complementary split-ring resonators and dielectric resonators. I will show that it is possible to achieve energy absorption with approximately 100% efficiency. Simulation and experimental results will be provided to fully validate the feasibility and practicality of electromagnetic energy harvesting using metasurfaces.
Biography: Omar M. Ramahi was born in Jerusalem, Palestine. He received the BS degrees in Mathematics and Electrical and Computer Engineering (Highest Honors) from Oregon State University, Corvallis, OR. In 1990, he was awarded the Ph.D. degree in Electrical and Computer Engineering from the University of Illinois at Urbana-Champaign. He worked at Digital Equipment Corporation (presently, HP), where he was a member of the Alpha Server Product Development Group. In 2000, he joined the faculty of the James Clark School of Engineering at the University of Maryland at College Park as an Assistant Professor and later as a tenured Associate Professor. At Maryland he was also a faculty member of the CALCE Electronic Products and Systems Center. Presently, he is a Professor in the Electrical and Computer Engineering Department, University of Waterloo, Ontario, Canada. He has authored and co-authored over 330 journal and conference technical papers on topics related to the electromagnetic phenomena and computational techniques to understand the same. He is a co-author of the book EMI/EMC Computational Modeling Handbook, (first edition: Kluwer, 1998, Second Ed: Springer-Verlag, 2001. Japanese edition published in 2005).
Professor Ramahi is the winner of the 2004 University of Maryland Pi Tau Sigma Purple Cam Shaft Award. Professor Ramahi won the Excellent Paper Award in the 2004 International Symposium on Electromagnetic Compatibility, Sendai, Japan, and the 2010 University of Waterloo Award for Excellence in Graduate Supervision. In 2012, Professor Ramahi was awarded the IEEE Electromagnetic Compatibility Society Technical Achievement Award.
Professor Ramahi served as a consultant to several companies and was a co-founder of EMS-PLUS, LLC and Applied Electromagnetic Technology, LLC, and the Eastern Rugs and Gifts Company. Dr. Ramahi is an elected IEEE Fellow. In 2009, he served as a Co-Guest Editor for the Journal of Applied Physics Special Issue on Metamaterials and Photonics. From 2007-2015, he served as an Associate Editor for the IEEE Transactions on Advanced Packaging. From 2010-2012, he served as an IEEE EMC Society Distinguished Lecturer. In 2014, he served as a Guest Editor for the journal Sensors, special issue on Metamaterial-Inspired Sensors.
Keynote Speaker 2