Linearization of GaN HEMT-Based Power Amplifiers Using a Bias Tracking Digital Predistortion

In this paper, a novel bias tracking (BT) digital predistortion (DPD) scheme for the compensation of charge-trapping effects in GaN HEMT -based power amplifiers (PAs). In the BT DPD scheme, a piece-wise polynomial (PMP) model is proposed in the digital domain to model the compensation bias voltage that is injected into the P A's gate bias and mask the gain changes caused by long-term charge-trapping effects. The proposed BT compensation method was demonstrated with a series of pulse-modulated LTE signals on a class-AB GaN HEMT-based P A. Measurement results indicated the proposed BT DPD scheme outperformed the conventional DPD method in linearization performances.