Multiplexers and their integration with crystal video receivers

Broadband, highly selective, low-loss contiguous multiplexers have been developed in the form of suspended-substrate-stripline (SSS) devices. These multiplexers can have channel bandwidths covering at least an octave (up to a decade for the lowest-frequency channel) with a passband insertion loss less than 1 dB and stopband attenuations greater than 60 dB within only 5% of the crossover frequencies. Moreover, these devices can be made extremely thin and lightweight; typically, a diplexer covering an octave band per channel weighs less than 15g. The suspended-substrate-stripline approach enables the direct integration of other microwave components onto the substrate to produce complete high-performance subsystems. A DC-coupled crystal log video receiver weighing only 230 g and enclosed in a 7.5 in3 box has been produced to cover the bands 4¿8, 8¿12 and 12¿18 GHz using the above ideas.