Digital Predistortion Using Extended Magnitude- Selective Affine Functions for 5G Handset Power Amplifiers with Load Mismatch

Load mismatch often occurs in radio frequency (RF) power amplifiers (PAs) in handset, which can complicate the nonlinear behavior of the transmitter, particularly when the voltage standing wave ratio (VSWR) is high. To effectively linearize handset PAs with load mismatch, in this article, we propose a low-complexity digital predistortion (DPD) model. After carefully analyzing the characteristics of handset transmitters with standing waves, we extend the magnitude-selective affine (MSA) function to construct nonlinear modeling terms in the DPD model. The new terms can effectively compensate for the distortion caused by load mismatch. Experimental results demonstrate that the proposed extended MSA (EMSA) model not only improves the modeling performance but also lowers the hardware complexity considerably, compared with the conventional models. The new model can thus serve as a good candidate for DPD deployment in 5G handset transmitters, where nonlinear behavior is more complicated and hardware resource is highly constrained.