Power Efficient RF Self-Interference Cancellation System for Simultaneous Transmit and Receive

Mono-static full duplex systems employ a single antenna and a circulator to provide isolation between the transmit (Tx) and the receive (Rx) radio chains. As much as 50 dB isolation is required to avoid receiver desensitization due to leakage of high power transmit signal. However, available circulators are typically designed to provide ~20-30 dB Tx/Rx port isolation. Therefore, additional cancellation circuits are required to enable simultaneous transmission and reception (STAR). In this paper, we present a novel STAR system that incorporates two circulators, a hybrid coupler, and a Self-Interference Cancellation (SIC) circuit based on a hybrid Finite Impulse Response (FIR) and a resonator topology. Preliminary simulations show promising results with an average Tx/Rx port isolation of 55 dB across a 20 MHz bandwidth.