Abstract
Highly directive antennas with beam steering capabilities are needed to overcome high path-loss, mitigate against interference from unwanted signals and to ensure network connectivity for the next generation 5G millimetre wave communication systems. Phased arrays using phase shifters are the conventional approach of achieving beam steerable antennas. However, due to the insertion loss incurred by phase shifters and the high cost of acquiring phase shifters, alternative solutions that offers lower loss and cost are being researched. This work proposes two beam steerable antenna solutions that offer reduced insertion loss and cost. The first beam steering solution is a novel passive amplitude steering antenna that makes use of a reconfigurable ratio power divider instead of the conventional variable gain amplifiers for amplitude control. The designed antenna is a 2X1 antenna array which achieves continuous steering over the range 0 degree to 21 degrees in one direction. The second beam steering solution combines the parasitic steering technique with the phased array approach to form a hybrid parasitic antenna. The hybrid parasitic antenna was formed from a 3X1 phased antenna array surrounded by eight parasitic elements. The parasitic elements are operated by switches and the antenna achieved a fine steering resolution of 1 degree. Computer simulations were performed to assess the effect of using real switches and phase shifters within the antenna. To this effect, 3-bit phase shifters were incorporated into the hybrid parasitic antenna and its performance compared with that of a conventional 3X1 phased array incorporating 5-bits phase shifters. The realised gain of the hybrid parasitic antenna was 4 dB better than that of the conventional phased array. This suggests that the novel antenna offers significant improvement in antenna performance. This work also proposed a novel approach that improves the isolation bandwidth of a power divider which will be vital for phased arrays and MIMO applications. The compensated power divider achieves a 15 dB isolation bandwidth of 114% which is more than 40% of the isolation bandwidth of conventional Wilkinson power divider. This power divider solution is suitable for ultra-wideband frequency applications.