Wideband Cavity-Backed Slot Subarray Fed by Gap Ridge Waveguide for 5G mmWave Base Station

This paper proposes a bandwidth-improved cavity-backed unit cell slot subarray antenna fed by a gap ridge waveguide for Line-of-Sight (LoS) SG mmWave applications. The proposed subarray is comprised of three layers. The top layer is the antenna layer in a 2 x 2 slots configuration, the cavity layer is in the middle and the ridge gap waveguide feeding is in the bottom layer. We propose to enhance the bandwidth of the unit cell subarray antenna by modifying the coupling slot in the cavity layer. The main advantage of the proposed method is that the bandwidth enhancement can be achieved without adding an extra tuning pin in the cavity layer, which eases mass production. The proposed structure is simulated with the CST software in an infinite array environment. The simulation results show that the S-11 is below-10 dB over 24 - 31.5 GHz frequency band covering a 27% bandwidth and the directivity is approximately 33.8 dBi when evaluated as a 16 x 16 element slot array. It is envisaged that the method can be advantageous for bandwidth enhancement of a practical cavity-backed slot array antenna.