Base-band predistortion linearization scheme of high efficiency power amplifiers for wireless applications

The paper shows the impact of a base-band predistortion linearization scheme of high efficiency power amplifiers (HPAs) in terms of key parameters such as the adjacent channel power ratio (ACPR) and the average PA efficiency. Two HPAs are compared: an uneven GaN Doherty (DPA) and a 2nd harmonic tuned Si LD-MOS (LPA). The base-band behavioral models of the HPAs are based on the parallel Hammerstein approach, while the digital predistorter (DPD) is extracted employing the nonlinear autoregressive scheme with exogenous inputs. For the DPA with a W-CDMA signal with 3.5 dB peak to average power ratio (PAPR), the predistorter is capable of a 10 dB ACPR reduction, without decreasing the average efficiency, but the DPD effectiveness quickly degrades with high PAPR signals and back-off levels. Different behavior is observed for the LPA where the increase of the PAPR do not affect the DPD effectiveness. While fed with an extremely demanding W-CDMA 3GPP standard, the amelioration of the overall HPA performance in terms of back-off and efficiency are better than 10 dB of back-off and better than 15% concerning the average efficiency.