Class-iF-1: Linearity Enhanced High Efficiency Power Amplifier

This paper presents a new class of power amplifier (PA) - Class-iF(-1)- resolving the highly nonlinear double inflection characteristics in the conventional Class-F-1 PA. It is illustrated that, by properly terminating the second harmonic source impedance (Z(2S)) from conventional short-circuit to open-circuit, the double inflection nonlinear gain profile can be mitigated in the proposed Class-iF(-1) PA, wherein the same saturation output power is achieved with less gain compression without drain efficiency trade-off. The idea was validated with source/loadpull and a broadband prototype operating from 2.0 to 2.6 GHz was designed using a commercial 10-W Gallium Nitride (GaN) transistor. Under continuous wave (CW) signal test, the proposed Class-iF(-1) a PA can achieve 40.1-40.8-dBm output power, 71.2%-77.3% drain efficiency (DE) and 67.4%-74.1% power added efficiency (PAE) at 3-dB gain compression level over 2.0-2.6 GHz.