Adaptive Digital Predistorter for Radio Frequency Power Amplifier Linearization

Power amplifiers (PAs) are inherently nonlinear devices and are used in almost all communications systems. Adaptive digital predistortion is a highly cost-effective way to linearize PAs, and can be implemented by using several ways, which include rational function. This paper presents a rational function based adaptive digital predistorter (RF-ADP) for PA linearization based on the indirect learning architecture. The RF-ADP models amplitude nonlinearity and phase nonlinearity of the predistorter with rational functions. After systematic analysis on the proposed RF-ADP, a low computation complexity adaptive algorithm using least-mean-square is deduced to update coefficient vectors for the inverse amplitude response and forward phase response from the amplitude and phase response at the PA output, respectively. Finally, several computer simulations are done to evaluate the performance of the proposed RF-ADP, and the results show the proposed RF-ADP is very efficient to improve the PA linearity.