Design of Microstrip Low-Pass–Bandpass Multiplexers Using Distributed Coupling Technique

In this paper, a five-channel low-pass-bandpass frequency quintplexer and a five-channel low-pass-bandpass frequency triplexer are presented. The multiplexer consists of a long distributed coupling feeding line, output feeding lines, a low-pass filter, and four bandpass channel filters. To validate the design concept, the two multiplexers are designed, fabricated, and tested, where the simulation results agree well with measurement results.