Power Adaptive Digital Predistortion for Wideband RF Power Amplifiers With Dynamic Power Transmission

Abstract

To reduce power consumption of wireless transmitters, the transmission power level of RF power amplifiers (PAs) may dynamically change according to real-time data traffic. This leads that the existing digital predistortion (DPD) techniques cannot be directly employed because they are mainly suitable for eliminating distortion induced by the PAs operated at a relatively stable condition, e.g., at a constant average power level. To resolve this problem, a power adaptive DPD is proposed in this paper. By accurately modeling the behavior change pattern of the PA with the input power adjustments and embedding it into the DPD model, the proposed DPD system is able to adjust its coefficients to adapt to the behavior variation of the PA induced by the power adjustments without real-time recalibration. A low-complexity online coefficients updating method is also proposed to track the behavior change of the PA caused by other factors, such as bias shifting or temperature variation, during real-time operation. Measurements with a high power LDMOS Doherty PA have been used to validate the proposed approach. Results show that the proposed DPD and its coefficients updating approach can produce excellent performance with very low complexity compared to the conventional approaches.