DESIGN OF HIGH-EFFICIENT POLARIZATION CONVERSION METASURFACE

Abstract

Metasurfaces are artificially engineered structures that are proposed to employ the phase, amplitude, and polarization of the electromagnetic (EM) wave. Among many properties, polarization conversion of the EM wave is the main attraction among the scientific community because of its vast application, especially in the defense industry. The usage of metasurfaces for radar cross section (RCS) reduction and stealth optimization has recently emerged due to their low profile, light-weight structure, and compact characteristics as compared to conventional radar absorbing materials which are complex to implement and expensive to maintain. Moreover, their relative ease of fabrication and low cost make them attractive for RCS reduction applications. In this thesis, a novel, wideband RCS reduction metasurface is presented based on polarization conversion. The proposed unit element is composed of a double arrowhead structure sandwiched with an inner circular ring in an array with its mirror elements rotated at 90 degrees for polarization conversion. This results in RCS reduction due to polarization conversion in reflective mode. The unit cell and its mirror operate as a cross polarizer from 7.6-12.6 GHz. The metasurface is implemented in a 15×15 array on an FR4 substrate and Polyimide Substrate with thickness of 0.3mm and 0.1mm and an overall dimension of 7×7 inches. The proposed surface's RCS was computed and compared with a ground plane of an identically sized metallic flat plate. Fabricated metal surface exhibits broadband bandwidth and reduction of 10 dB RCS from 8-12 GHz with a peak RCS reduction of 20.83 dB. The measured results agree with the simulated data and hence show the actual polarization conversion efficiency of the metasurface.