20, 30 GHz Band Cassegrain Earth Station Antenna for the Japanese Domestic Satellite Communication System

An 11.5 m 30/20 GHz band Cassegrain antenna has been developed for a Japanese domestic satellite communication system earth station. In order to form an economical satellite communication network, the earth station antenna is required to be installed on the top of a telephone office building in a large city. Therefore, interference with terrestrial radio relay systems and antenna load on a building become the most important problems to be investigated. Considering the satellite position in geostationary orbit, a limited steerable system combined with a two-jackscrew drive mechanism is employed to lighten and simplify the antenna structure. Measured antenna aperture efficiencies are 72% in 20 GHz band and 68% in 30 GHz band. Measured wide angle radiation patterns satisfy the CCIR recommendation level. The of the antenna at the feed horn port is measured to be 53.9 dB/K at at 18.75 GHz. Interference with the 20 GHz band terrestrial radio relay system in extremely near field was experimentally studied. Results show that the terrestrial system\´s antennas can be installed closely up to about 20 m without serious interference.