Real-Time Adaptive Transmitter Leakage Cancelling in 5.8-GHz Full-Duplex Transceivers

This paper describes the design principles for a real-time adaptive transmitter leakage canceller and introduces its training algorithm for fast adaptation. The canceller implements the active feed-forward analog cancelling technique, which considers the injection at the receiving input of the self-interfering antiphase signal. An extensive characterization carried out on a prototype designed to operate at the center frequency of 5.8 GHz demonstrates the performance of the prototype in term of cancellation and tracking convergence speed, and confirms the validity of the canceller design principles. Measurements at 5.8 GHz show that for isolation between the transmitting and receiving antenna up to 35 dB with arbitrary phase, an isolation above 60 dB is obtained in 98.5% of the tests and this result is reached in six steps. When applied to a wireless transceiver for electronic-toll collection system operating in full duplex at 5.8 GHz under regulation European Telecommunications Standards Institute ES200674, the prototype permits a signal-to-noise-ratio enhancement of 8.3 dB.