First-pass design of high efficiency power amplifiers using accurate large signal models

A systematic, first-pass methodology for designing high efficiency power amplifier (PA) using only large signal CAD models is presented. Detailed analysis using the model reveals significant insights into PA operation as well as the required impedance environment for high efficiency mode of operation. In particular, waveform engineering and empirical loadpull are used to determine the optimal class of operation and impedance terminations. Combined with the use of precise electromagnetic simulator in synthesizing the matching network, first pass design of a 10W, 3.3 GHz GaN inverse class F PA as well as a 2.5 GHz push-pull inverse class F PA was realized with very good agreement between simulation and measurement results. Specifically, the 3.3 GHz PA achieved 74% power added efficiency (PAE) at 3.27 GHz with 38.27 dBm output power, while the push-pull PA achieved 75% drain efficiency with 42.7 dBm output power. The linearizability of the 3.3 GHz PA is demonstrated using predistorted WiMAX modulated signals. When combined with DPD, the PA showed acceptable EVM for use in next generation wireless base stations.