A Multifunctional Frequency-Selective Polarization Converter for Broadband Backward-Scattering Reduction

A novel dual-polarized frequency-selective polarization converter (FSPC) with low-backward scattering is proposed by combining a bandpass frequency-selective surface (FSS) with a polarization converter. The FSPC, comprised of the top polarization conversion layer and the bottom multilayer bandpass FSS, is formed by introducing two polarization converter bands on both sides of the broadband passband. The four-port equivalent circuit model cascading FSS and polarization converter is proposed and investigated. It is numerically demonstrated that a flat 1 dB transmission window can be obtained from 8.5 to 11 GHz with a 25.6% fractional bandwidth (FBW), and the bandwidth of reflection below −10 dB is up to 92% from 5.6 to 15.13 GHz. Moreover, the proposed device can achieve two polarization conversion bands (5.66–6.9 and 12.8–15.2 GHz) with the polarization conversion ratio over 90%. Besides, by arranging the proposed structure in a checkerboard-like distribution, the backward scattering energy can be reduced in a wide frequency band ranging from 4.5 to 16 GHz. Both simulation and experimental results are in good agreement, which demonstrates our design strategy. Compared with the conventional polarization converters, the proposed design presents an extra frequency-selective performance and, hence, can be a great substitute for the frequency-selective rasorber (FSR).