High-efficiency cross and linear-to-circular polarization converters based on novel frequency selective surfaces

Most high-efficiency polarization converters in literatures are based on reflective structures. Here we report the designs and experiments of high-efficiency transmissive polarization converters using novel compact frequency-selective surfaces (FSSs). By combining the common dipole and square ring based band-pass FSSs, a novel FSS can be generated, whose high-efficiency pass bands and transmissive phases for two orthogonal polarizations can be tuned by changing the dimensions of the FSS structure. As demonstrations of the concept, a transmissive cross polarization converter (a half-wave plate) and a transmissive linear-to-circular polarization (LP-CP) converter (a quarter-wave plate) are designed and tested, respectively. Simulated results show that the polarization conversion ratio over 90% for the transmissive cross-polarization converter is from 18.5 to 23.5 GHz, about 23.8%, and the 3-dB LP-CP conversion bandwidth is 19.6%. Experiments are carried out to validate both designs.