Microwave Microstrip Six-Channel Triplexer and Eight-Channel Quadruplexer

This paper presents two microstrip multiband multiplexers using distributed coupling technique. The proposed multiband multiplexers consist of a distributed coupling feeding line, asymmetric stepped-impedance resonators, and output feeding lines. Each pair of resonators controls a respective bandpass channel for good design freedom. By using distributed coupling technique, there is no extra matching network required in the multiplexers. In order to obtain a wide stopband, asymmetric stepped-impedance resonators and asymmetric feeding lines are employed. The operation frequencies of the first multiband multiplexer are at 1, 1.3, 1.6, 1.9, 2.2, and 2.5 GHz, and the second one operates at 1, 1.3, 1.6, 1.9, 2.2, 2.5, 2.8, and 3.1 GHz. The stopband rejection level is better than 20 dB up to 4.6 times the lowest operation frequency. The proposed design concept is validated with the two fabricated multiband multiplexers. The measurements show good agreement with simulations.