A Wideband Tightly Coupled Slot Antenna for 360° Full Azimuthal Beam Steering Applications

A single-layer planar coupled-slot antenna is presented for 360° azimuthal beam scanning applications over a wide frequency band. Eight sets of antennas each consisting of three tightly coupled slots cover the full azimuthal plane. Tightly coupled slots provide wide bandwidth with minimum gain variation in the endfire direction. Two antenna configurations are presented. The first antenna with eight independent ports is suitable for multiple-input multiple-output (MIMO) systems. The second antenna uses a single excitation port. Eight radiators are sequentially switched using a feed network with p-i-n diodes to cover the whole azimuth plane. Prototypes of the antennas are fabricated. Both of them operate over 8.8-11.2 GHz with input matching better than 10 dB and a gain variation within 4.95 dBi ± 0.25 dBi, including the feed loss.