Blind digital tuning for interference cancellation in full-duplex radio

To make full-duplex radios, the most fundamental challenge known today is self-interference cancellation. This paper takes a new look at digitally controlled all-analog interference cancellation channel consisting of clustered taps (c-taps) of step-attenuators and other passive components such as RF power combiners and dividers. The performance of such a cancellation channel is robust to carrier frequency and attenuation-dependent phases of attenuators. Without the cost for and the errors from down-converting the input RF waveforms of any of the attenuators, a blind digital tuning algorithm based on the residual interference waveforms collected during a training phase is shown to be promising.