Broadband waveplate operation by orthotropic metasurface reflector

We present an anisotropic metasurface offering a simultaneous linear to cross-polarization conversion and linear to circular polarization conversion operations on large bandwidths of microwave frequencies. The proposed orthotropic structure consists of metallic bow tie shaped patches with embedded circular patches enabling diagonal structure symmetry. We demonstrate through numerical simulations and experiments that the metasurface can be used as a high efficiency linear to cross-polarization reflective converter within the two broad frequency bands of 7.48–10.55 GHz and 18.47–19.52 GHz with a polarization conversion ratio above 90%. Simultaneously, the designed metasurface acts as a circular polarizer for linearly polarized incident waves in triple frequency bands of 6.10–7.46 GHz, 10.55–18.42 GHz, and 19.60–22.39 GHz with an axial ratio below the 3 dB threshold. To the best of our knowledge, the second band from 10.55 to 18.42 GHz of circular polarization conversion “has the highest reported (to date) bandwidth of 54.3% for an axial ratio below 3 dB.” The designed metasurface remains angular stable up to 75° over most of the part of the above-mentioned operating bands for both transverse-electric and transverse-magnetic polarized wave incidences.