A Ka-band circularly polarized (CP) waveguide slot antenna with a cross iris is proposed. To achieve the CP characteristic (LHCP) in the antenna, a hexagonal shaped cavity is used. The impedance matching is improved by adjusting the sizes of the hexagonal cavity and a rectangular matching cavity. To enhance the axial ratio bandwidth, a cross iris is used with two arms of different lengths. From experimental results, the proposed antenna has a 3 dB axial ratio bandwidth of 6810 MHz (31.72 GHz–38.53 GHz). The −10 dB reflection coefficient bandwidth of the proposed antenna ranges from 31.51 GHz to 39.21 GHz (7700 MHz).
Design of Circularly Polarized Waveguide Slot Antenna of Microstrip-Appended