A Low Profile Planar Dual-Polarized Tightly Coupled Dipole Reflectarray With 5:1 Bandwidth

This work introduces an extremely low profile ( $0.4\lambda _{high}$ ) planar ultra-wideband dual-polarized reflectarray. The unit-cell structure of the array is modular in nature, and without any electrical connection between adjacent unit-cells. The array uses tightly coupled dipoles arranged in an egg-crate fashion connected with true-time-delay lines. This array provides the required phase in the highest ever reported bandwidth of 5:1 (3 to 15 GHz) with VSWR< 2.5 for a planar reflectarray. The implementation of the delay-lines is done using a sandwich configuration between two conductive planes, which significantly improves the cross-polarization purity of our reflectarray. To validate our design concept, an $18\times 18$ element ( $135\times 135$ mm) reflectarray is designed, fabricated, and measured. The measurements exhibit excellent agreement with the simulations.