Open-Loop Digital Predistorter for RF Power Amplifiers Using Dynamic Deviation Reduction-Based Volterra Series

TLDR

The paper proposes an efficient open‑loop digital predistorter based on dynamic deviation reduction Volterra series to compensate nonlinear distortion and memory effects in RF power amplifiers. The predistorter’s parameters are extracted via offline system identification, and its design is compared to a memoryless polynomial predistorter with analysis of decrement effects. The approach eliminates the need for closed‑loop adaptation, further reduces complexity through undersampling and parameter interpolation, and experimentally achieves substantial nonlinear distortion reduction as evidenced by improved adjacent channel power ratio and normalized RMS error.

Abstract

In this paper, we propose an efficient open-loop digital predistorter (DPD) derived from the dynamic deviation reduction-based Volterra series that allows compensation for both nonlinear distortion and memory effects induced by RF power amplifiers in wireless transmitters. In this approach, the parameters of the predistorter can be directly extracted from an offline system identification process. This eliminates the usual requirement for a closed-loop real-time parameter adaptation, which dramatically reduces the implementation complexity of the system. It is shown that a further reduction in system complexity can be achieved by applying under-sampling theory in the model extraction and utilizing parameter interpolation in the DPD implementation. Experimental results show that by utilizing this technique with only a small number of parameters, nonlinear distortion induced by the PA can be significantly reduced, as evaluated by both adjacent channel power ratio reduction and normalized root mean square error improvement. A comparison with a memoryless polynomial function based predistorter and an analysis of the impact of decresting are also presented.