Dual-band capacitively loaded annular-ring slot antenna for dual-sense circular polarization

Abstract This paper investigates a simplified and new capacitively loaded annular-ring slot antenna (ARSA) for dual-band and dual-sense circular polarization. The antenna is comprised of two concentric annular-ring slots coupled to a microstrip feed line to achieve dual-band operation. With introducing proper distributed capacitances fulfilled by two closely spaced T-shaped arc strips across the outer and inner annular-ring slots at opposite positions with respect to the microstrip feed line, the dual-sense circular polarization can hence be obtained. The antenna features that the impedance and circular polarization characteristic for the upper band can be independently adjusted. Numerical analysis and experimental validation have been carried out. The measured 10-dB return loss impedance bandwidths for both bands are greater than 22.0%. The measured 3-dB axial ratio (AR) bandwidths are 3.6 and 5.6%, respectively, for the lower and upper bands.