Impact of Input Nonlinearity on Efficiency, Power, and Linearity Performance of GaN RF Power Amplifiers

The impact of input nonlinearity due to the nonlinear C
GS
-
$V$
GS
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
2S
) termination with an efficiency delta of ∼40%. In contrast, Class F
^−l
PA shows relatively robust performance with an efficiency delta of ∼10% versus Z
2S
terminations. Thus, we identify the ‘good’ and ‘bad’ design space of Z
2S
terminations on the Smith chart for load harmonic tuned PA classes. In addition, this paper identifies a design space continuum for Z
2S
terminations other than a short for Class F
^−l
PA which results in consistent efficiency, output power, and improved linearity.