A tunable 0.86–1.03 GHz FDD wireless communication system with an evanescent-mode diplexer and a self-interference-cancelling receiver

A tunable multiband FDD system is presented in this paper. For the first time, a tunable evanescent-mode cavity diplexer and a 65 nm CMOS self-interference-cancelling receiver are combined to provide high Tx-to-Rx isolation required in a multiband FDD system. Self-interference-cancellation reduces the required filter order for a given Tx-to-Rx isolation, reducing the loss associated with the tunable filter. The system has a measured tuning range of 0.86–1.03 GHz with 45 dB Tx-to-Rx isolation bandwidths of 4 MHz, at low band, and 2 MHz at high band. Simultaneous transmission and reception using 16-QAM signals are also demonstrated, showing the feasibility of using the presented system in a realistic tunable FDD system.