A W-Band Choke-Ring Encircled Focal Plane Array of Full-Metal Elements for Reflector Antennas With Over 50%-Efficiency High Crossover Beams

This letter presents a novel W-band [(92 to 96) GHz] focal plane array (FPA) for 50 dBi reflector antennas intended for the next-generation point-to-point communication links with antenna mast sway compensation. The FPA comprises seven metal waveguide elements arranged in a hexagonal lattice, ensuring the crossover level of the corresponding reflector beams above $-\text{6}$ dB. The primary challenge of this design is to realize efficient illumination of the reflector for the on-axis and off-axis beams, while keeping a minimum beamforming complexity (i.e., one element per beam) and overcoming array implementation challenges associated with high frequencies. This is accomplished by a high decoupling level of the FPA elements ($< -\text{24}$ dB) and shaping their individual element patterns via a dedicated aperture pin structure between them, and encircling the FPA aperture with a periodically perforated choke ring pair to further improve the illumination by offset elements. The FPA performance, evaluated on an offset parabolic reflector with $F/D=0.35$, exhibits 52%–68% efficiency, close beam overlap, and good impedance matching. Measurements of the FPA prototype verify the results for all characteristics; the latter are competitive with state-of-the-art solutions.