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Multiple-Beam Focal-Plane Dual-Band Fabry–Pérot Cavity Antenna With Reduced Beam Degradation

Focal-plane reflector feeds with shared aperture are a promising solution for the increasing number of beams required in the Ka-band satellite services. Stringent manufacturing tolerances and coupling between feeds tend to penalize performance, which is aggravated for a dual band. This paper proposes a new design of a shared aperture antenna intended for multispot single-feed-per beam satellite applications that allows recovering single-feed performance, minimizing the usual impact of adjacent feeds on the field distribution and ultimately on the antenna directivity and gain. We present a new focal-plane dual-band Fabry–Pérot cavity antenna (FPCA) design, which allows more reliable fabrication, closer agreement with simulations, and larger bandwidth than the reported solutions. It uses only one double-sided printed frequency-selective surface (FSS) to form the dual-band FPCA, and it is fed through a novel arrangement of double-layer slots in the FPCA-printed ground plane. This favors impedance matching and higher isolation between adjacent feeds. The effectiveness of the solution is experimentally demonstrated for a single-feed Ka-band (20 and 30 GHz) prototype. The generalization for a complete multifeed configuration with filters is shown by full-wave simulations. The decoupling slots on the FPCA ground plane enable restoring single-feed performance in the multifeed system, over the bandwidth of interest.