Digital compensation of RF nonlinearities in software-defined radios

The wideband RF receiver in a software-defined radio (SDR) system suffers from the nonlinear effects caused by the front-end analog processing. In the presence of strong blocker (interference) signals, nonlinearities introduce severe cross modulation over the desired signals. This paper investigates how the nonlinear distortions can be compensated for by using digital signal processing techniques. In the proposed solution, the SDR scans the wide spectrum and locates the desired signal and strong blocker signals. After down-converting these signals separately into the baseband, the baseband processor processes them jointly to mitigate the cross-modulation interferences. As a result, the sensitivity of the wideband RF receiver to the non-linearity impairment can be significantly lowered, simplifying the RF and analog circuitry design in terms of implementation cost and power consumption.