Effects of Digital Predistortion and Crest Factor Reduction Techniques on Efficiency and Linearity Trade-Off in Class AB GaN-PA

Crest Factor Reduction (CFR) technique based on peak windowing scheme in conjunction with Digital Predistortion (DPD) technique using Generalized Memory Polynomial (GMP(DPD)) are studied, and their effect on the efficiency-linearity trade-off in Class-AB GaN power amplifier (PA) driven by multicarrier WCDMA signals is reported. Experimental results show that CFR can reasonably reduce the peak to average power ratio (PAPR) of the input signals, allowing an improvement of the PA efficiency. Proper match of CFR with DPD techniques can allow the PA to be driven deeper into saturation, resulting in achieving higher efficiency without compromising its linearity. The proposed method had been applied to a 10W class AB GaN PA resulting in an average efficiency improvement between 40%-50% while maintaining Adjacent Channel Power Ratio (ACPR) and Error Vector Magnitude (EVM) within the specifications of the used standard.