LAUSR

This paper proposed a wideband, efficient, and high gain circularly polarized (CP) array antenna based on the gap waveguide technology for 30 GHz frequency band applications. The antenna subarray is a $2 \times 2$ slot groove gap waveguide-based cavity-backed antenna. The antenna is fed by a ridge gap waveguide (RGW). Two corners of the radiating slots are truncated to obtain CP radiation, and some corrugations are introduced to the radiating layer to suppress the surface waves between neighbor subarrays. The planar 16-way feeding network based on RGW is utilized to feed the subarrays. The feeding network is multilevel sequential phased with a quadrature phase shift. To validate the array antenna performance, a prototype of the antenna has been manufactured using standard milling technology. The measured reflection coefficient bandwidth is about 22% covering from 28.3 to 35.3 GHz, and a measured 3 dB axial ratio bandwidth of about 21.8% is achieved from 27.8 to 34.6 GHz. The maximum measured gain is 23.5 dBi which is occurred at 30.75 GHz.