A dichroic subreflector for a communication satellite

The authors present results of a study involving the design, manufacturing, and test of a large (1.1-m) dichroic subreflector for an offset Cassegrain reflector antenna. The primary focus feed operates at 10.7-11.7 GHz, and the secondary feed operates at 18.1-20.2 GHz, both with linear orthogonal polarizations. A preliminary design of the dichroic structure using an equivalent circuit approach showed that, given the desired closeness of the transmission and reflection bands, double-layer frequency selective surfaces with single resonant elements were the most promising configuration. Two layers of crossed dipoles with an interlayer distance of about 5 mm were selected. Results for electrical performance tests are presented.<>