2015-Numerical and Experimental Verification of a 3D Quasi-Optical System.pdf

Research Article Numerical and Experimental Verification of a 3D Quasi-Optical System Zejian Lu,1 Xiaoming Liu,1 Hai Wang,1 Xiaodong Chen,2 Yuan Yao,1 and Junsheng Yu1 1School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China 2School of Electric Engineering and Computer Science, Queen Mary University of London, London E1 4NS, UK Correspondence should be addressed to Zejian Lu; lzj bupt@ Received 26 January 2015; Revised 9 May 2015; Accepted 10 May 2015 Academic Editor: Atsushi Mase Copyright ? 2015 Zejian Lu et al.This is an open access article distributed under theCreative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A modular and efficient Gaussian beam (GB) analysis method, incorporating frame-based Gabor transformation, GB reflection, and a 3D GB diffraction technique, was developed to analyze both the reflectors and frequency selective surface (FSS) in quasi- optical (QO) system. To validate this analysismethod, a 3Ddual-channelQO systemoperating at 183 and 325GHzwas designed and tested. The proposed QO system employs two-layer structure with a FSS of perforated hexagonal array transmitting the 325GHz signal on the top layer while diverting the 183GHz signal to the bottom layer. Measured results of the system demonstrate that the agreement can be achieved down to ?30 dB signal level for both channels in the far field pattern. The discrepancy between the calculation and measurement is within 2 dB in the main beam region (2.5 times ?3 dB beamwidth), verifying the effectiveness and accuracy of the proposed method. 1. Introduction Quasi-optical network (QON) system normally consists of several feed horns and cascaded mirrors or other signal- conditioning components. A QON transmits electromag- netic waves in free space, bearing advantages ofmultichannel, multipolarization with low path loss and good compatibil