Digitally Assisted RF-Analog Self Interference Cancellation for Wideband Full-Duplex Radios

This brief presents a new approach to cancelling self-interference in full-duplex radios. By augmenting minimal-complexity analog cancellation hardware using a radio frequency vector multiplier with the flexibility and effectiveness of a digital baseband rational function finite impulse response (FIR) filter, the proposed approach enables excellent cancellation performance over a wide modulation bandwidth. This algorithm is devised by exploiting a simplified baseband equivalent behavioral model of the front-end of the full-duplex radio. This allows the parameters of the rational function FIR filter to be identified linearly using the least-squares estimation. The hardware proof-of-concept prototype, built using off-the-shelf components, demonstrated minimum self-interference cancellations of 50 and 40 dB for digitally modulated test signals with modulation bandwidths of 20 and 40-120 MHz, respectively.