A new microstrip duplexer using open circuited dual-behavior resonator

This paper describes a new microstrip duplexer based on open-circuited dual-behavior resonator (OC-DBR). The duplexer offers transmission zeros´ location at the out-of-band response by controlling the impedance ratio of their OC-DBRs, leading to high isolation duplexer design. The proposed duplexer is designed and fabricated on RF60-0600 substrate to suit for the UMTS communication applications with the 1.92-1.98GHz downlink and 2.11-2.17GHz uplink frequencies. Across the bandwidth, the measured insertion losses at the both bands are less than 1.6dB, while the input and output return losses are well below 10dB. More than 30dB isolation performance is obtained from the prototype duplexer.