Generalized Continuous Class-F Harmonic Tuned Power Amplifiers

This letter generalizes the theory of continuous class-F harmonic tuned power amplifiers (PAs) to model their operation for gate bias voltages above the pinch-off point (i.e., class-AB bias conditions). The proposed theory starts with deriving intrinsic drain current and voltage waveforms for continuous class-F harmonic tuned PA biased above pinch-off and then finding the resulting design space. The new formations resulted in shifted fundamental impedance space along with expanded second harmonic impedance space as the conduction angle, α, is swept between 180 and 360°. Moreover, under class-F harmonic tuned termination, it is found that the drive power required at the input of the device is also dependent on bias conditions. For experimental validation, the proposed approach is adopted to implement a broadband PA using a 10 W gallium-nitride (GaN) transistor. Under class-AB bias conditions, the implemented PA shows more than 70% power added efficiency, 40 dBm output power, and 15 dB gain at frequencies from 550 to 950 MHz.