A Software-Defined 1TX/2RX FDD Transceiver Employing Frequency-Selective Dual-Band Self-Interference Cancellation

This paper presents a software-defined 1TX/2RX frequency-division duplex (FDD) transceiver front-end employing frequency-selective dual-band self-interference cancellation (SIC) allowing simultaneous transmit-and-receive operation in close proximity wireless channels. A tunable RF tap and an multi-tap baseband FIR filter are incorporated in tandem to suppress the Tx self-interference in the Tx band and in two symmetric adjacent channels in which reception takes place, respectively. The FIR filter's weights are computed based on a dual-band least squares algorithm, which closed-form expressions are derived in detail. Measurement results of an FDD front-end prototype demonstrate a total of 90 dB cancellation in both Rx bands simultaneously, with 40 dB of passive isolation due to the leakage channel's attenuation and 50 dB by the active FIR canceller.