Synthesis of unequally spaced array using multi-stage differential evolutional algorithm

Design of an unequally spaced linear array with pencil beam and low peak sidelobe level (PSLL) is one of the most important optimization problems. An antenna array with pencil beam and low sidelobe offers promising capacity for space division multiple access system, which also offer a robust implementation against multipath propagation effects. However, most researchers have only focused on either the main beam width or the PSLL. In this paper, a multi-stage differential evolutional algorithm (MSDEA) is proposed to jointly optimized the null to null beam width (NNBW) of the main beam, the PSLL and the power efficiency by using a modified objective function. The simulation results indicate that the MSDEA algorithm outperforms conventional DEA in terms of NNBW and power efficiency. For 32 elements antenna array, it achieves 3.78° NNBW with 100% power efficiency. The effect of optimization using initial phase is also discussed.