Channel multiplexers for broadcasting satellite transponders in the 12 GHz band

The design and fabrication results for a two-channel input multiplexer and a four-channel output multiplexer for broadcasting satellite transponders are described. The requisite characteristics of channel multiplexers are discussed. The filter for the input multiplexer, which requires a narrow band and steep out-of-band attenuation characteristics, is composed of an eight-pole canonical dual-mode filter and a coupler. The geometry and design of these units are described. The output multiplexer is composed of four-pole elliptic dual-mode filters which use higher-order resonant mode with high unloaded Q; the geometry of this filter is described. Causes of the decrease in unloaded Q in a coupled cavity filter are discussed, and aspects of the four-channel multiplexer and filter based on these loss considerations are examined.