Real-time FPGA-based baseband predistortion of W-CDMA 3GPP high-efficiency power amplifiers: Comparing GaN HEMT and Si LDMOS predistorted PA performances

We carry out a comparative design study on two high-efficiency power amplifiers (a second-harmonic tuning LD-MOS and a Doherty GaN-based amplifier) linearized through baseband digital predistortion so as to comply with the W-CDMA 3GPP standard with acceptable efficiency. Several predistortion schemes (both memoryless and with memory) were tried, having in mind the final FPGA implementation. The results, besides highlighting some interesting features of the two amplifiers considered, show that significant improvements can be achieved in the Power Added Efficiency (PAE) even starting from a highly efficient but poorly linear power stage.