Low-Profile and Wideband Dual-Circularly Polarized Reflect-Arrays Based on Rotated Metal-Backed Dual-Polarized Aperture-Coupled Patch Elements

In this article, the theory, design, and experimental verification of low-profile and wideband dual-circularly polarized (dual-CP) reflect-arrays (RAs) with independent handedness-based beamforming are reported. Such functionality is enabled by simultaneously exploiting the dynamic phase and Berry phase compensation techniques, which is illustrated mathematically by deriving the required conditions for the reflection coefficient matrix of the dual-CP RA phasing elements. Different from previously proposed multifunctional layer RAs for controlling waves with different handedness, here the independent dual-CP phase shifting is accomplished with only a single functional layer of elements. As proof-of-concept examples, rotated metal-backed dual-polarized aperture-coupled patches, with a profile of lower than 0.3 lambda(0), are designed, providing 2 x 2 bit dual-CP phase shifting that can offer independent beamforming of left-/right-handed CP (LHCP/RHCP) waves with an LHCP/RHCP feed antenna. Utilizing the proposed dual-CP elements, two specific dual-CP RAs operating in the Ka-band are synthesized, fabricated, and characterized, achieving either symmetrical or asymmetrical dual-CP beams over a wide bandwidth. The experimentally measured peak gain is higher than 28 dBic, while the joint axial ratio <2 and 1 dB gain bandwidth is wider than 14.7%, for both dual-CP RAs. The generalized design methodology and the demonstrated dual-CP RAs are highly useful for a variety of wireless and satellite communication systems.