Design of Quasi periodic and Aperiodic Array Lattices to Improve Array Antenna Performance

Abstract

quotThe thesis addresses one of the possible solutions to the grating lobe occurrence in the beam steerable periodic arrays for large angular beam scans. The controlled aperiodicity has been introduced to the periodic array to achieve the same and the object is set to design the beam steerable array antenna offering improvement in the peak SLL performance with beam scan and reducing the number of array elements. The designs of such aperiodic and quasi-periodic array antennas have been carried out using the innovative strip projection (SP) based method. The strip projection method uses the area of rotated higher dimensional lattice and projects it to lower dimensions to generate an aperiodic array. The designs of aperiodic linear and planar arrays have been carried out to achieve ±30° conical beam scan range with peak SLL lt-10dB over -90° to 90o angular range. The novelty of the proposed SP method is that the number of optimization variables is fixed and independent of the size of the aperiodic array. The reported techniques to generate the aperiodic arrays lack in this aspect. The proposed method facilitates a significant reduction of the design efforts, especially in the case of the larger beam-steerable arrays. The proposed method is relatively straightforward to implement compared to the reported algorithms. newlineThe performance of the aperiodic linear array antenna has been compared with the aperiodic arrays designed using evolutionary optimization algorithms, namely, genetic algorithm (GA), particle swarm optimization (PSO) and Jaya algorithms and it is found that the proposed design method is comparatively more efficient and faster. The aperiodic array lattice is also populated with X-band electromagnetically coupled patch antenna integrated with a phase shifter and simulated. The aperiodic patch array antenna has been fabricated and characterized in the anechoic chamber. The comparison of the measured and simulated results is presented.