Dual‐band dual‐sense circularly polarized antenna for S‐ and C‐band applications

This paper presents a dual‐band dual‐sense circularly polarized (CP) antenna for S‐ and C‐band applications. A semicircular patch and a circular slot are first designed to achieve wide operation bandwidth in the C‐band with right‐hand CP (RHCP), and then, a curved slot is properly inserted around the circular slot for S‐band realization with left‐hand CP (LHCP). Final antenna prototype has an overall size of 0.32 λ L  × 0.32 λ L  × 0.01 λ L , where λ L is free‐space wavelength at the lowest CP frequency. Experimental results show that good CP characteristics for both RHCP and LHCP can be achieved. The measured −10 dB impedance bandwidth is from 2.2 to 6.5 GHz, equivalent to about 98.8%. Additionally, the measured 3 dB axial‐ratio bandwidths for lower and upper bands are, respectively, 4.9% (2.4‐2.52 GHz) and 40.8% (4.0‐6.05 GHz).