On the Cross-Polarization Levels of Arrays With Wide Angle Impedance Matching Layers

The characteristic cross-polarization (X-pol) of wide angle impedance matching (WAIM) structures is investigated. The study considers an ideal linearly polarized current sheet in the presence of various dielectric and artificial dielectric superstrates, analyzed using transmission line models representing the stratified media. The main mechanism that causes increased X-pol is highlighted and linked to the anisotropy of the superstrate. We then propose an approach to reduce the X-pol by including vertical vias within the WAIM dielectrics, to control the vertical component of the permittivity tensor. The intrinsic X-pol performance of a set of artificial dielectric layers (ADLs) with and without vias is experimentally verified by placing the WAIM above an open-ended waveguide that acts as a linearly polarized source. The proposed WAIM with vias can be used in wideband wide-scanning array designs to improve polarization purity.