A Ka-Band Circularly-Polarized Filtering Antenna Array with A Hybrid Feeding Network

A circularly-polarized filtering antenna array is designed in 23~27.5 GHz. Its hybrid feeding network is built up hybridly with stripline and air-filled substrate integrated waveguide (AFSIW) structures, for both antenna efficiency and design flexibility. The filtering response is achieved by stacked patch radiators, embedded stripline lowpass filters, the AFSIW network and a substrate integrated waveguide bandpass filter. The stripline-fed 4×4 subarrays are fabricated and measured. For the whole 16×16 array, the simulated in-band realized gain is 23.03~26.31 dBi, the out-of-band suppression is higher than 23.29 dB, and the x-polarized suppression is better than 31.13 dB.