A circularly polarized antenna based on EMSIW sub-array with high front-to-back ratio

A high front-to-back ratio circularly polarized planar antenna is presented in this communication based on a quarter-mode substrate integrated waveguide sub-array. It is composed of three parts: an eighth-mode substrate integrated waveguide (EMSIW) sub-array, four coaxial cables which are used to connect the probe-fed sub-array and the corporate feed network, and the feed network of which composed three Wilkinson power dividers is applied to feed the array. The measured front to back radiation ratio and the measured antenna gain for right-hand circular polarization (RHCP) are 28.6 dB and 6.61 dBi at 5.2 GHz, respectively. The measured 10-dB return loss and 3-dB axial ratio bandwidths at the center frequency 5.2 GHz are 21.53% and 10.96%, respectively.