Load-Mismatch Tracking Digital Predistortion for Mobile-Terminal Power Amplifiers

In this paper, a novel load-mismatch tracking digital predistortion (DPD) technique is proposed for linearizing mobile-terminal power amplifiers (PAs) under varying load-mismatch conditions. A time-domain poly-harmonic distortion (TD-PHD) model is discussed first for the behavioral modeling and linearization of PA under mismatch, followed by a practical model construction method. Then, the proposed DPD technique is derived based on the superposition principle, which enables automatic and fast adjustments of its coefficients to adapt to the PA's nonlinear characteristics under different load-mismatch conditions without re-identification of the DPD model. Experimental validations on a mobile-terminal PA module at 4.6 GHz with a 100 MHz 5G NR signal show that the proposed DPD technique realizes excellent linearization performance among a wide load-impedance varying range with low complexity.