Ultra-wideband cross polarization conversion metasurface insensitive to incidence angle

A broadband microwave cross-polarization-conversion (CPC) metasurface is designed, simulated, fabricated, and tested. The metasurface consists of coupled split-ring-resonators (SRRs) with two splits in each SRR and is designed on an FR4 dielectric substrate backed by a metallic ground plane. An efficient CPC, both for normal as well as for oblique incidence, is achieved with 3 dB fractional bandwidth of 73% from 5 to 10.8 GHz. This wideband polarization conversion results from multiple plasmonic resonances occurring at three neighboring frequencies. Owing to the sub-wavelength unit cell size and symmetric structure of the coupled SRRs, the response of the metasurface is independent of the polarization and incidence angle of the incoming wave, which makes it a potential candidate for many practical applications. The proposed design is validated both numerically and experimentally. Experimental results are found to be in good agreement with simulations.