Design and Experiment of a Single-Feed Quad-Beam Reflectarray Antenna

Reflectarray antennas show momentous promise as a cost-effective high-gain antenna, capable of generating multiple simultaneous beams. A systematic study on various design methods of single-feed multi-beam reflectarray antennas is presented in this communication. Two direct design methods for multi-beam reflectarrays, geometrical method and superposition method, are investigated first. It is demonstrated that although both methods could generate a multi-beam radiation pattern, neither approach provides satisfactory performance, mainly due to high side-lobe levels and gain loss in these designs. The alternating projection method is then implemented to optimize the phase distribution on the reflectarray surface for multi-beam performance. Mask definition and convergence condition of the optimization are studied for multi-beam reflectarray designs. Finally a Ka-band reflectarray prototype is fabricated and tested which shows a good quad-beam performance.