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

This paper proposes an approach to improve performance of a dual-circularly polarized (CP) patch using non uniform 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 capacitive couple between the patch and the parasitic elements also introduces a new coupling path flowing on the parasitic elements, which is opposite to the original coupling path between two ports. A weak-field area is therefore generated, and the isolation is improved. It is also worth noting that by using non-uniform parasitic elements, wide isolation bandwidth can be attained. The fabricated antenna prototype with overall dimensions of 0.83 λ × 0.83 λ × 0.03 λ has measured operating bandwidth of 17.8% (5.1– 6.1 GHz). Across this band, the isolation is always higher than 20 dB, and the broadside gain is from 5.2 to 7.6 dBi.