A broadband resonant cavity antenna with circular polarization (CP) and high gain characteristics is presented. Its primary radiator comprises of two bowtie dipoles, which are arranged orthogonally and then incorporated with double vacant printed rings to generate wideband CP radiation. A half-wavelength planar partially reflecting surface is utilized to achieve high-gain broadside radiation, and wide axial ratio (AR) as well as gain bandwidths. The antenna with an overall size of approximately 2?? × 2?? × 0.7?? at 7.4 GHz yields measured ?10-dB impedance and 3-dB AR bandwidths of 40% and 25.6%, respectively. Experimental results also showed an average gain of 14.5 dBic over the CP operating bandwidth and a 3-dB gain bandwidth of 42.7% (5.7?8.8 GHz).
