A 30 GHz band band-splitting filter for satellite communication earth station

The channel-dropping filter using the TE-01 mode semicircular waveguide has been utilized for the 30 GHz band at an earth station because of its low-loss and high-power tolerance characteristics. A small-size band-splitting filter, using the TE-01 mode semicircular waveguide, has been newly developed. This diplexer consists of semicircular branch-guide hybrids and high-pass filters. Construction and operation principle of the diplexer are described. Semicircular branch-guide hybrid length is about 100 mm, one-third that of a coupled wave type hybrid. Branching characteristics of the diplexer for dividing the 27.5-31.0 GHz frequency band into two equal bands, have proved tolerably flat, with a resulting branching loss amounting to as little as 0.5 dB. Total diplexer length is about 800 mm. It is concluded that the semi-circular branch-guide diplexer can be effectively used for a satellite communication earth station.