Design of broadband reflecting metasurfaces for polarization conversion

A broadband linear polarization converter based on a reflecting metasurface is presented. The polarization converter is composed by a periodic arrangement of metallic particles, positioned in a square lattice with a periodicity T equal to 4.6mm. The metallic elements are printed on a metal-backed Rohacell HF31 layer with a thickness of 3mm. The unit cell topology is optimized by using a genetic algorithm. The polarization converter works from 7.3 GHz to 29.01 GHz. Since the genetic algorithm provides arbitrary cell geometries where surface currents are not excited, a refinement procedure is proposed for removing unnecessary pixels. The highest working frequency polarization converter obtained at the end of the refinement process is extended up to 32.88 GHz thus obtaining a relative bandwidth of 129.54%.