A five-frequency radiometer antenna system feed horn

The feasibility of operating a five frequency feed as a radiometer for use on board a Nimbus type satellite was investigated. Five narrow band frequencies (6.6, 10.7, 18.5, 21.5 and 33 GHz) were multiplexed onto a single receive feed employing dual linear polarization at each frequency with a better than 25 db isolation between each polarization. The production of a horn design which can illuminate a parabolic reflector segment with an f/D ratio of approximately 0.4, producing an edge illumination of approximately -20 db is described. The final overall design is presented with results showing that this design concept has an acceptable electrical performance.