Multi‐Beam and Shaped‐Beam Reflectarray Antennas

This chapter presents a systematic study on various design methods of multi‐beam and shaped‐beam reflectarray antennas. It describes direct design methods for multi‐beam reflectarrays, the geometrical method and the superposition method. The chapter demonstrates that although both methods can generate a multi‐beam radiation pattern, neither approach provides satisfactory performance, mainly due to high side‐lobe levels and gain loss in these designs. It introduces synthesis design techniques, and two different optimization techniques, the alternating projection method and the particle swarm optimization method, are then implemented to optimize the phase distribution on the reflectarray surface. The chapter also presents several examples of shaped and multi‐beam reflectarray antennas. Reflectarrays can generate single or multiple pencil‐ or shaped beams with single or multiple feeds, and several designs have been presented over the years. In addition to the multiple beam designs introduced earlier that use a single‐feed antenna, reflectarrays can also achieve a multi‐beam performance by using multiple feed antennas.