The Design Technique for Coaxial Resonator Cavity Duplexer

A general design technique for the coaxial resonator cavity duplexer is proposed in this paper, based on the design method of the general Chebyshev band-pass filter. We can obtain the coupling matrixes of cross-coupled resonator duplexer by optimization technique, and complete the design of duplexer fast. The proposed duplexer is designed and fabricated with the 1.92–1.98 GHz downlink and 2.11–2.17 GHz uplink frequencies. Across the bandwidth, the measured insertion losses at the both bands are less than 1 dB, while the input and output return losses are well below 20 dB. More than 50 dB isolation performance is obtained from the duplexer. The measured results approximately meet all the conditions of the design targets.