I. I NTRODUCTION M ODERN communication systems are continuously evolving to fulfill the growing users’ demand for faster transmission rate and data capacity, leading to broader signal bandwidth, high-order modulations, and high peak-to-average power ratio (PAPR). The requirements for the linearity of the transmission signal are more stringent, and higher energy

The power amplifiers (PAs) often suffer from load mismatch in mobile terminals due to the complicated working environments, making linearizing those PAs a challenging task. This article proposes a novel load-mismatch tracking digital predistortion (LMT-DPD) technique for linearizing mobile-terminal PAs under varying load-mismatch conditions. The time-domain polyharmonic 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 LMT-DPD technique is derived based on the superposition principle. According to the real-time load reflection coefficients, the LMT-DPD enables automatic and fast adjustments of the predistorter to adapt to the PA ’s nonlinear distortion under different load-mismatch conditions without coefficient recalibration. Experimental validations are carried out on a mobile-terminal PA module at 4.6 GHz with a 100-MHz 5G new radio (NR) signal. The test results show that the proposed LMTDPD technique can significantly reduce the update frequency of predistorter while realizing excellent linearization performance.

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