Planar RF Duplexer with Multiple Levels of Transfer-Function Reconfigurability

This paper reports on the RF design of planar RF duplexers with unprecedented levels of transfer-function adaptivity. These reconfiguration capabilities include center-frequency tuning, bandwidth (BW) tuning, and intrinsic RF switching-off. The proposed RF duplexer concept is based on the connection of two three-pole/two-transmission-zero (TZ) bandpass filters (BPFs) that exhibit fully-reconfigurable quasi-elliptic-type transfer functions, so that they can be exploited for the independent control of its transmit and receive channels. For experimental-validation purposes, a microstrip RF duplexer prototype was designed, manufactured, and measured in the 1.4-2 GHz band. Its channels show center-frequency tuning ratio of 1.3:1, BW tuning ratio of 5:1, and can be intrinsically switched-off in an independent way.