Augmented Volterra predistortion for the joint mitigation of power amplifier and I/Q modulator impairments in wideband flexible radio

Dynamic and flexible RF spectrum access through software-defined radio technologies is known to be limited by transmitter RF impairments, most notably spurious emissions due to mixer I/Q imbalance and power amplifier nonlinearity. In this article, a novel digital predistortion structure is developed for joint mitigation of frequency-dependent I/Q imbalance and dynamic nonlinear effects of amplifiers in wideband direct-conversion radio transmitters. The developed structure consists of two Volterra series in parallel, with built-in sparsity in the kernels, and is shown to be linear in parameters thus requiring only one feedback path for joint parameter identification. Extensive simulation results demonstrate significant improvements in transmitter linearization performance, compared to state-of-the-art memory polynomial based linearizers. Thus, the developed predistortion solution can be seen as one key enabling technique towards practical deployment of SDR technology with digitally-enhanced wideband RF front-ends.