Single-Feed Quad-Beam Transmitarray Antenna Design

We present a design methodology for single-feed multibeam transmitarray antennas through case studies of quad-beam designs. Different far-field pattern masks and fitness functions are studied for multibeam designs, and the particle swarm optimization (PSO) technique is implemented for aperture phase synthesis. A quad-layer configuration of double square loops is used for the transmitarray elements, and a quad-beam transmitarray prototype is fabricated and tested. The effects of various approximations in unit-cell analysis are also investigated in detail. The Ku-band prototype generates four symmetric beams with 50° elevation separation between the beams and gains around 23 dB.