A novel electronically tunable active duplexer for wireless transceiver applications

In this paper a novel electronically tunable active duplexer suitable for reconfigurable wireless transceiver applications is presented for the first time. The theory, design, and measured results of a varactor tunable active duplexer are summarized. The prototype active duplexer presented in this paper provides an electronically adjustable isolation of 20 to 50 dB between isolated ports and a constant gain of 5 dB between coupled ports in the tunable range from 1.62 to 1.82 GHz in both transmit and receive modes of operations. The design guidelines as well as measured S-parameters of the duplexer are presented. The proposed duplexer can be easily implemented as an MMIC.