3-D Bifocal Design Method for Dual-Reflectarray Configurations With Application to Multibeam Satellite Antennas in Ka-Band

This paper describes a 3-D bifocal design technique for offset dual-reflectarray antennas (DRAAs) with application to multibeam satellite antennas in Ka-band. The bifocal technique has been used to obtain beams closer than those obtained with a single-focus antenna and, at the same time, to improve the performance of the extreme beams. The technique has been applied to design a multibeam DRAA in an offset compact range configuration to provide 1.12° separation between adjacent beams at 19.7 GHz. A small-scale bifocal DRAA demonstrator has been designed, fabricated, and tested. The demonstrator generates 10 beams alternating in dual-linear polarization when the antenna is illuminated by five adjacent feeds, but the technique can be extended to circular polarization. The results are in a good agreement with the design requirements in the frequency band from 19.2 to 20.2 GHz.