Anisotropic-Impedance-Surface-Based Broadband Dual-CP Polarization Optically Transparent Reflectarray Using Fine Metal Line

In this letter, a dual-circularly polarized (dual-CP) optically transparent reflectarray (RA) antenna operating in the Ka-band is proposed. The RA cell utilizes an anisotropic imped- ance surface (AIS) configuration and features an ultrathin profile of approximately 0.1125λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>. The RA element features highly effici- ent deflection of reflected waves without altering polarization properties. By adjusting size parameters and rotation angles, both dynamic phase and Berry phase can be applied, providing dual-CP phase compensation insensitive to incident angle. To validate this concept, the optically transparent RA antenna with independently controllable beamforming was designed, analyzed, and experimentally measured. Measurements show that the 3-dB gain bandwidth reaches 33.7% and 30.3% for Right-hand CP (RHCP) and Left-hand CP (LHCP) wave, respectively. And axial-ratio bandwidth (ARBW) reaches 53.3%. The antenna's gain and aperture efficiency (AE) attain 32.21/32.42 dBic and 32.6%/34.3% for CP incident waves.