Wideband Circularly Polarized Cavity-Backed Asymmetric Crossed Bowtie Dipole Antenna

A single-feed, cavity-backed, circularly polarized (CP) antenna is designed for wideband wireless applications. The antenna is made up of asymmetric crossed bowtie dipoles and achieves broadband characteristics in terms of impedance and 3-dB axial-ratio (AR) bandwidths. A double vacant-quarter printed ring with orthogonal asymmetric bowties is employed for CP radiation and then combined with slot-mode radiation to significantly enhance the CP operation bandwidth. Measurements of an optimized antenna prototype with an overall size of 0.88A lambda(0), x 0.88 lambda(0) x 0.23 lambda(0),, at 2.4 GHz show that it can yield an impedance bandwidth of approximately 57% and a 3-dB AR bandwidth of approximately 51%. In addition, a unidirectional CP radiation pattern with a high broadside average gain of 9.6 dBic was achieved across the operating bandwidth.