加州大学洛杉矶分校许慎恒博士来我系参加教师应聘讲座

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发布时间：2011-06-10 浏览次数：4395

电子科学与技术系教师应聘讲座

加州大学洛杉矶分校电气与计算机工程系

许慎恒博士

时间：6月16日上午10点

地点：电信大楼305室

Reflectarray Antennas and Applications in Reflector Surface Distortion Compensations

Abstract

Large reflector antennas have been widely used in satellite communications, radar systems, remote sensing and radio astronomy applications. Due to the limitations on manufacture and assembly accuracy, thermal effects in outer space, and gravitational effects on large ground stations, reflector surface distortions are inevitable. A small amount can cause considerable performance degradations, which need to be overcome using special compensation techniques. Recently microstrip reflectarray antennas have attracted a lot of interests because of some favorable features such as high performance, ease-to-manufacture, light weight and low profile. Individual reflectarray elements can produce an optimized wavefront with pre-designed phase shifts to achieve pencil beam, shaped beam or electronically scanned beam. In this seminar I will propose a novel reflector surface distortion compensation technique by utilizing the direct phase controlling capability of reflectarray. A reflectarray antenna acts as a subreflector. By adjusting the reflection phases of reflectarray the scattered wavefront is optimized so that the phase errors caused by main reflector surface distortions can thus be compensated. Conjugate field matching method is used to determine the reflection phases and a graphical visualization of reflectarray phases is used to analyze and diagnose reflectarrays. Two examples, feed defocusing and a ring-type surface bump of a 1.2-m symmetric reflector antenna, are chosen to validate the proposed method. Two reflectarrays are designed, simulated, fabricated, and measured, respectively. HFSS/Physical Optics hybrid method is used in computer simulations. The reflector/reflectarray system is measured in the bi-polar near-field anechoic chamber. Remarkable improvements are accomplished in both simulations and measurements.

Biography

XU, Shenheng, received the B.E. and M.E. degrees from Southeast University in 2001 and 2004, respectively, and the Ph.D. degree in Electrical Engineering from the University of California, Los Angeles (UCLA) in 2009. From 2001 to 2004 he was a Research Assistant in the State Key Laboratory of Millimeter Waves at Southeast University. In 2004, he joined the Antenna Research, Analysis and Measurement Laboratory at UCLA, where he currently works as a postdoctoral researcher. His research interests include novel designs of modern reflector and reflectarray antennas for advanced applications, various compensation techniques for reflector antennas, electromagnetic and antenna theories, and evolutionary optimization algorithms for electromagnetic applications. He is a member of IEEE and the recipient of 2008 NASA Tech Brief Award.