A Quadrature Balanced Multi-Mode RF Front-End Architecture with Wideband Ultra Low Power Self Interference Cancellation

This paper presents a quadrature balanced RF Front-End architecture with a built-in primary isolation for a single antenna Full Duplex and Time Division Duplex wireless communications. Self-interference cancellation is implemented by injecting a digitally synthesized cancellation signal into a dedicated input port that enables wideband cancellation of the leaking transmit signal at the receiver. A closed form analytical expression of the cancellation signal as a function of the channel frequency response is derived, together with a nonlinear analysis that predicts distortion fundamentals at both transmit and receive channels. Simulations at the 5-6GHz Wi-Fi band verify the theoretical results and demonstrate leakage cancellation better than 60dB for 160MHz and 320MHz channels for linear and nonlinear operation conditions.