Current Trends and Approaches to improve Self-Interference Cancellation at the RF Domain across a Wide Bandwidth

To double spectrum efficiency, a well-known approach uses simultaneous transmit and receiver (STAR) radios. The goal is to suppress the coupling from the transmitter to the receiver, using the knowledge of the transmitted signal. Successful implementation of STAR requires self-interference cancellation of at least 100 dB across the entire band. Notably, sufficient isolation between the Tx/Rx signal must be achieved to avoid saturation in the LNA and other components in the Rx chain. In the past, STAR realizations were narrowband. This paper presents current trends and approaches to achieve improved Tx-Rx isolation across a wideband channel of 1 GHz, as required by 6G and future applications. Measurements show that a combined 2-stage isolation of > 65 dB can be achieved.