Development of a High-Efficiency Circularly Polarized Ka-Band Satcom Antenna Utilizing Ridge-Loaded U-Shaped Radiator

This letter presents a low-profile, high-gain cavity-backed slot array antenna, based on ridge gap waveguide (RGW) technology, to operate within the Ka frequency band. The antenna array consists of two layers. The upper layer incorporates an array of U-shaped slots, positioned over a cavity loaded with a metal ridge section, while the lower layer is a RGW corporate distribution network, feeding each of the cavity-backed slots separately with equal phase and amplitude. The proposed array antenna radiates circularly polarized waves (axial ratio below 3$ \text{ dB}$) over a bandwidth of 8.6$ \%$ ranging from 27.5$ $ GHz to 30$ \, \text{ GHz}$. At the centre frequency of 28.75 GHz, the peak gain at the broadside direction is 27$ \text{ dBi}$ and the first relative sidelobe level is below −13$ \text{ dB}$. The total size of the proposed 8 × 8$ $-element array antenna is 6.7$ \lambda _{0} \times $ 6.5$ \lambda _{0} \times $ 1.4$ \lambda _{0} $.