The Design of Novel Pattern Reconfigurable Antennas for Mobile Networks

This research evaluates a beam reconfigurable basestation transceiver for cellular applications from both a systems and antenna design perspective. The novelty in this research is the investigation of an automatic azimuth beamwidth switching antenna, which can effectively respond to homogeneous traffic distribution in a cellular mobile network. The proposed technique which this antenna uses is azimuth beam switching which incorporates PIN diodes to provide a reconfigurable reflecting ground plane for a three sector antenna. Numerical systems analysis has been carried out on a hexagonal homogeneous cellular network to evaluate how this reconfigurable antenna can balance mean and cell edge capacity through azimuth beamwidth reconfiguration. The optimum azimuth beamwidth is identified as 60°, which achieves the best cell capacity, and by reconfiguring the azimuth beamwidth from 60° to 110°, the maximized capacity at the edges of the cell can be improved. The influence of mechanical tilt, inter site distance, path loss model and vicinity of the cell edge for this antenna are described. This research shows that a mean cell edge improvement from 15Mbit/s to 18Mbit/s is achievable when beamwidth reconfiguration is used, and that this improvement is consistent for cell sizes from 500m to 1500m. Results from a test of an as-manufactured reconfigurable antenna are presented here, and show similar results compared to simulations. To overcome network coverage deterioration at large antenna downtilt angles in a homogeneous cellular mobile network, different beam shaping techniques in the elevation plane, including antenna sidelobe suppressing and null filling, are discussed here. By filling up the first upper-side null for a 12-element antenna array, both the average cell edge and cell capacity can be improved. The application of this beam shaping pattern for a 12-element array is described here, for the purpose of optimising a specific cell within a mobile network which is shown below average coverage and/or capacity. By choosing a proper antenna downtilt angle for this specific cell, whilst keeping the optimum tilt angle for other cells in the network, the cell’s coverage/capacity can be increased without impacting too much on the performance of other surrounding cells. Lastly, the effects of number of antenna elements for a 60° azimuth beamwidth antenna array on the network coverage/capacity are discussed here. This research shows that, as a result of an increasing number of antenna elements in an elevation direction, network capacity can be increased along with the optimum tilt angle. This suggests that a high gain antenna array in a cellular mobile network can be potential for large site deployment and fewer installations