Single-Layer Reflectarray Antenna With Independent Dual-CP Beam Control

This letter presents a single-layer dual-circular-polarization reflectarray antenna with independent beam control for each polarization. First, a novel phasing approach, combining the variable-size approach and the element rotation approach together, is theoretically devised to achieve independent phase shifts for left hand circular polarized antenna (LHCP) and right hand circular polarized antenna (RHCP) waves. Then, a single-layer nested split-ring element has been designed as an example, and independent 360 degrees phase shift for each circular polarization has been achieved. Finally, a Ka-band (20 GHz) reflectarray prototype with a circular aperture of 390 mm in diameter is designed, fabricated, and tested. Independent pencil beams radiating to the predesigned directions for each polarization were achieved. The measured gain is 35.5 dBi at -30 degrees with the aperture efficiency of 52.7% for the LHCP excitation, and the measured gain is 35.4 dBi at 30 degrees with the aperture efficiency of 51.6% for the RHCP excitation. The measured 1 dB gain bandwidths are 10.5% (19.4-21.5 GHz) and 10.0% (19.5-21.5 GHz) for the LHCP and RHCP excitations, respectively.