A Compact Microstrip Duplexer

In this paper, a compact microstrip duplexer with relatively close channels is proposed. The ring resonator and the orthogonal-feed are directly connected to form a band elimination filter. The band elimination filter is loaded with branches to realize the band-pass filter. The design of the duplexer in the article composed of two such band-pass filters. The design method of the duplexer is introduced in detail, and verified by the experimental results of the manufactured duplexer. The central frequency of the bandpass channels is 1.45Ghz and 1.75Ghz respectively. The measurement results show that the two channels of the duplexers are close to each other, with low insertion loss and high out-of-band rejection, which are in good agreement with the simulation results.