Wideband High-Isolation Dual-Circularly Polarized Co-Aperture Antenna Using Nonuniform Parasitic Elements

This letter proposes an approach to improve performance of a dual-circularly polarized (CP) patch using nonuniform parasitic elements. To overcome the limited operating bandwidth and poor isolation of the conventional dual-CP patch, multiple parasitic elements are used to produce additional resonance to improve the operating bandwidth. Interestingly, the use of parasitic elements makes the phase centers of the right-hand CP and left-hand CP states close to each other. Accordingly, high isolation can be obtained. It is also worth noting that by using nonuniform parasitic elements, wide isolation bandwidth can be attained. The fabricated antenna prototype with overall dimensions of 0.83λ × 0.83λ × 0.03λ has measured operating bandwidth of 17.8% (5.1 GHz to 6.1 GHz). Across this band, the isolation is always higher than 20 dB, and the broadside gain is from 5.2 dBi to 7.6 dBi.