An anisotropic impedance surface for dual-band linear-to-circular transmission polarization convertor

A transmission polarizer is described that is based on an anisotropic impedance surfaces to convert the incident linearly polarized wave to a circularly polarized one. The polarizer is based on a frequency selective surface (FSS) with two concentric rings having cuts at different orientations/angles. By virtue of anisotropy it is possible to independently control the transmission characteristics of two orthogonal linearly polarized incident plane waves and therefore to achieve polarization conversion in the transmission direction. A unit cell approach with periodic boundary conditions is considered in the design environment; this unit cell incorporates the two concentric rings. The proposed topology supports in achieving dual-band polarization conversion, which has advantages over previously reported designs. The polarizer works at 27.2 GHz and 39.5 GHz and provides the required 90° phase difference between the two orthogonal components, which are equal in magnitude. The structure provides around 99% polarization purity at resonance. The linear performance of this new structure is described through results of numerical simulations.