Impact of Input Nonlinearity on Efficiency, Power, and Linearity Performance of GaN RF Power Amplifiers
Sagar K. Dhar, Tushar Sharma, Ramzi Darraji, Damon G. Holmes, Joseph Staudinger, Xin Yu Zhou, Vince Mallette, Fadhel M. Ghannouchi
Abstract
The impact of input nonlinearity due to the nonlinear C <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</inf> - <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V$</tex> <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GS</inf> profile on load harmonic tuned power amplifier (PA) performance is qualitatively discussed. It is experimentally validated by pulsed vector load pull measurements that both Class B and Class F PA operation are quite sensitive to the source second harmonic (Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2S</inf> ) termination with an efficiency delta of ∼40%. In contrast, Class F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−l</sup> PA shows relatively robust performance with an efficiency delta of ∼10% versus Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2S</inf> terminations. Thus, we identify the ‘good’ and ‘bad’ design space of Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2S</inf> terminations on the Smith chart for load harmonic tuned PA classes. In addition, this paper identifies a design space continuum for Z <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2S</inf> terminations other than a short for Class F <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−l</sup> PA which results in consistent efficiency, output power, and improved linearity.