Wideband Coffee-Bean Shaped Radiating Element for Circularly-Polarized Waveguide Slot Arrays

A wideband coffee-bean shaped radiating element for circularly-polarized waveguide slot arrays is presented. The proposed solution is based on a very simple polarizer aimed to be integrated into flat panel antennas in the millimeter-wave band. For validation purposes, a slot array fed by a groove gap waveguide network at 30 GHz is taken as a feeder. Simulated results using periodic boundary conditions in a 2×2 unit cell are presented in this work. Preliminary results show a frequency bandwidth of 4 GHz with input reflection coefficient better than -10 dB. It is worth stressing the good polarization purity achieved, being below 1.5 dB from 29 GHz to 31 GHz and below 3 dB in the whole band of interest (28 to 32 GHz).