Digital Nonlinear Processing for Simultaneous Transmit and Receive

The components that typically constitute a high performance simultaneous transmit and receive (STAR) architecture include some combination of RF isolation, analog subtraction and digital cancellation. Digital cancellation is the last line of defense in a STAR architecture, where cancellation performance is not only limited by the distortion and noise imparted by the passive and active components that precede it, but also by the peak-to-average power (PAPR) of the waveform itself. In this presentation I will present a detailed analysis of how transmit and receive impairments, including waveform dependent properties, limit digital cancellation performance. I then describe nonlinear approaches to model and remove the distortion and imbalance generated by RF and mixed signal components. Removing the distortion imparted by both transmitters and receivers as a part of the digital cancellation process facilitates high performance self-interference cancellation. Results from over-the-air tests are used to corroborate the impact of nonlinear digital baseband processing on STAR performance.