Electromagnetic Devices Based on Periodic Structures
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Recent research advances in periodic structures and antenna array systems operating at microwave frequencies will be presented. First part of the talk will cover frequency scanning phased-array feed networks and frequency selective surface (FSS) spatial filters based on metamaterial concepts. Composite Right/Left-Handed (CRLH) metamaterial delay lines provide not only phase delay but also phase advance response that can be systematically controlled. This dispersion engineering technique allows the design of an all-passive phased-array feed network that supports broadband frequency scanning capability over a wide spatial angle. In addition, decoupling the radiating antenna elements from the array factor enables better controllability of the far-field radiated characteristics in comparison to the widely known CRLH based leaky-wave antennas. Conventional periodic structures based on purely right-handed unit structures also exhibit metamaterial behavior when the periodicities are much smaller that the operating wavelength. Incorporating this miniaturized concept with coupled filter theory, high performance dual-pole FSSs can be designed that are less sensitive to incident angles, polarizations, and separation distances between the FSS layers. In the second half of the presentation, a state-of-the-art polarization friendly retrodirective array (RDA) will be presented. RDAs have the unique ability to transmit a received signal back toward the interrogator without prior knowledge of the interrogator's location. The proposed system can also receive any polarization and always backscatters the signal that is orthogonally polarized with respect to its received polarization state. This added feature helps to maintain a more stable communication link between the RDA and the interrogator by mitigating polarization mismatch loss.
Jun (Brandon) Choi received Ph.D. degree in Electrical Engineering at the University of California, Los Angeles, in 2014. He is now assistant professor in the Department of Electrical Engineering and Computer Science at the Syracuse University, NY. His research interests are in the areas of applied electromagnetics and microwave engineering. In particular, dispersion engineering, periodic structure analysis, and antenna/array theory have been extensively applied throughout his research works in developing novel microwave devices and systems