A Piecewise Interpolation Based Digital Predistortion of Power Amplifiers Across Wide Power Ranges

This paper presents a novel piecewise linear interpolation scheme to enable digital predistortion (DPD) for linearizing power amplifiers (PAs) across the wide power ranges required in massive multipleinput multiple-output (mMIMO) transmitters. By interpolating between DPD coefficients corresponding to a subset of average power levels, the proposed method reduces linearization complexity and eliminates the need for frequent DPD retraining at every power operating point. Theoretical derivations of the interpolation scheme are provided, followed by experimental validation on a Gallium Nitride (GaN) PA operating at 13 GHz. The results show that interpolating DPD coefficients at four different power levels over a 17 dB range achieved an Adjacent Channel Power Ratio (ACPR) and Error Vector Magnitude (EVM) of better than -44 dB and -38 dB, respectively. This provides a favorable balance between dedicated DPD training at each power level (ACPR and EVM of better than -47 dB and -42 dB) and using a single DPD set at peak power (ACPR and EVM of better than -37 dB and -28 dB). The proposed approach offers an efficient solution for scaling DPD with power while maintaining acceptable linearity.