A High Isolation and Low Loss Duplexer Based on SISL Platform

This paper presents a duplexer with high isolation and low loss based on the substrate integrated suspended line (SISL) platform. Both the two bandpass filters (BPFs) corresponding to the transmitter (Tx) and the receiver (Rx) bands are composed of a low-pass filter (LPF) and a high-pass filter (HPF). A matching network is designed to connect the two signal transmission paths with high isolation, and match to the antenna port. The simulated and measured results are in good agreement. The operating frequencies of the duplexer are 0.8 and 2.5 GHz, i.e. the deviation frequency is 1.7 GHz. The measured insertion losses of the pro-posed duplexer are 1.26/1.21 dB. Excellent isolation of over 60 dB is obtained. To further reduce the dielectric loss, we modify the design with patterned suspended substrate, and the improved duplexer shows a loss reduction of 0.23/0.25 dB at two operation bands. As compared with the reported works, the proposed SISL duplexer shows good performance in terms of low loss, high isolation, and self-packaging.