2.5D Frequency Selective Surface for Polarization‐Insensitive Cross‐Polarization Conversion

A 2.5D frequency selective surface with parallel double wires (FSSPDWs) is proposed for polarization‐insensitive cross‐polarization conversion. The unit cell of FSSPDWs consists of four identical resonant ring‐via‐resonant ring (RVR) modules. Each RVR module is composed of a shielded floor and a receiving resonance ring connected with a radiation resonance ring via parallel double wires and through‐hole structure. Parallel double wires with through‐hole structure function as vias. These vias transform the polarization converter into a 2.5D structure, generating multi‐resonant frequencies to achieve a wide bandwidth. To ensure insensitivity for arbitrary polarization, the unit cell of the FSSPDWs employs four rotationally symmetrical RVR modules. Simulated results demonstrate a cross‐polarization transmission coefficient exceeding −1dB in a wide band from 9.65 to 12.86 GHz (28%), with a polarization conversion rate (PCR) of more than 95% and an energy conversion rate (ECR) of greater than 93.5%. Additionally, the proposed FSSPDWs convert linear polarization to cross‐polarization at arbitrary polarized angles. The converter is manufactured and measured to validate simulations, showing good agreements between the simulated and measured results.