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Design of Single-Feed Reflectarray Antennas With Asymmetric Multiple Beams Using the Particle Swarm Optimization Method

Single-feed reflectarrays with asymmetric multiple beams are studied in this paper. The conventional methods for designing multibeam reflectarrays are first reviewed and the limitations of these approaches are delineated for asymmetric designs. A generalized design approach based on a global search optimization technique, namely the particle swarm optimization, is proposed for single-feed asymmetric multibeam reflectarray designs. Practical considerations in implementing a global search for phase optimization of reflectarrays with several hundreds of elements are addressed, and several designs of multiple beam reflectarrays with asymmetric beam directions and gain levels are presented. Furthermore, a single-feed asymmetric quad-beam Ka-band reflectarray prototype is fabricated and tested, which shows a good multibeam performance. This study demonstrates the effectiveness and robustness of the particle swarm optimization approach for designing complicated multibeam reflectarray antennas where conventional design approaches fail.