Broadband linear to circular polarization conversion over extreme angle of view using a single layer Frequency Selective Surface

Abstract

A single-layer Frequency-Selective Surface (FSS) is presented that splits the incident power equally in transmission and reflection. The FSS converts the linear polarization of the incident wave to circular polarization. The handedness of transmitted and reflected circularly polarized waves are orthogonal and it can be reversed by changing the linear polarization of the incident wave. The FSS is a single-layer patterned surface consists of rectangular patches that are connected by narrow strips from one side. The performance of the structure is evaluated using full-wave simulation. The proposed FSS exhibits a wide-band frequency response with a robust angular performance for up to 80° illumination angles. The transmittance/reflectance is $-3\pm 0.15$ dB, the axial ratio is smaller than $0.8$ dB and the phase difference is ${90}^o\pm {10}^o$ for both right-handed and left-handed circularly polarized scattered waves over all incident angles. Full-wave simulation of the structure demonstrates that the 3 dB axial ratio bandwidth is 85 %, 102 %, and 95 % for the reflected left-handed circularly polarized wave and 85 %, 104 %, and 125 % for the transmitted left-handed circularly polarized wave under TM and TE excitation by the incident angles $0^o,{45}^o,{\mathrm{and}80}^o$, respectively. The bandwidth and angular performance is enhanced compared to polarization converters demonstrated in recent literature. The proposed design presents a simple and low-cost solution to generate orthogonal handedness of circular polarization in both reflection and transmission with a wide bandwidth and a broad angular stability.