ACTIVE RF CANCELLATION OF NONLINEAR TX LEAKAGE IN FDD TRANSCEIVERS

In frequency division duplex (FDD) transceivers, transmitter (TX) passband leakage induced self-interference can cause own receiver (RX) desensitization, due to limited isolation of the duplexer RX filter and nonlinear components in the RX front-end. In this paper, an active RF cancellation technique for TX passband leakage is proposed, to efficiently suppress the nonlinear leakage signal at the RX chain input. The technique is based on generating an RF replica of the leakage signal using an auxiliary transmitter branch, together with appropriate digital preprocessing of the known transmit data. This RF replica is then combined with the received signal at the LNA input in the RX chain, properly phased, such that the level of the TX leakage signal is reduced. The performance of the proposed solution is evaluated with simulations as well as practical RF measurements, demonstrating excellent suppression of the TX leakage signal for wideband signals at high transmission power levels. Such novel self-interference cancellation solutions can facilitate enhanced efficiency and flexibility of the RF spectrum use in the emerging 5G radio networks, especially at the lower carrier frequencies.