Design of a New Waveguide Duplexer Based on Mode Matching Method

In order to further achieve the requirement of high isolation between frequency bands without increasing the size of the duplexer, this paper proposes a new type of waveguide duplexer. Based on the traditional diaphragm waveguide filter, the low-frequency filter of this duplexer uses a new waveguide CT-type inductive cross-coupling structure, and the high frequency filter introduces a non-resonant cavity structure. An S-band duplexer with a working frequency band of 2. 025-2. 12 GHz & 2. 2-2. 3 GHz is designed. According to the discontinuity of its structure, the mode matching method is used to quickly analyze and design. The duplexer has transmission zeros outside the high and low frequency bands of the passband. In the 2. 2-2. 3 GHz and 2. 025- 2. 12 GHz bands, the isolation is greater than 60 dB and 90 dB, and the return loss is greater than 20 dB. Compared with the traditional duplexer with the same performance, the duplexer has a small size and can be easily designed and widely used in engineering.