Design of a 600W Doherty using generation 2 HVHBT with 55% WCDMA efficiency linearized to −55dBc for 2c11 6.5dB PAR

A 2-way symmetrical Doherty amplifier achieving 600W saturated power has been developed using Generation 2 High-Voltage HBT (Gen 2 HVHBT) GaAs technology. In this paper we will show the development method used for this design work. From module optimization to final Doherty design this method is centered on highly accurate high power load pull. Operating at 28V the Doherty amplifier is capable of delivering 120W (50.8dBm) of linear power at a collector efficiency of 55% while achieving -55dBc linearized ACPR at 5MHz offset using a 2-carrier-side-by-side WCDMA signal having a peak to average ratio of 6.5dB (0.01% on CCDF). The linear power gain of the Doherty amplifier is 13.5dB, resulting in a final stage power-added efficiency of 53%. When stimulated with a CW signal the Gen 2 HVHBT Doherty amp achieves 500W (57dBm) at P1dB with a collector efficiency of 70% and 600W at saturated power with a collector efficiency of 72%. In the Doherty operating mode collector efficiency at an output back-off level of 6.5dB is increased by 20% points when compared to class AB operation.