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 that allows simultaneous transmit-and-receive operation in close proximity wireless channels using frequency-selective dual-band self-interference cancellation (SIC). The proposed front-end includes a tunable RF tap and a multi-tap baseband FIR filter to suppress the Tx self-interference in the Tx band and in two symmetric adjacent channels where reception takes place, respectively. The FIR filter’s weights are computed using a dual-band least squares algorithm, and closed-form expressions are derived in detail. Measurement results from an FDD front-end prototype show 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.