Exploring the Design Space for Broadband PAs using the Novel "Continuous Inverse Class-F Mode"

This paper presents a novel formulation for the inverse class-F mode of operation, termed the "continuous inverse class-F mode", resulting in an extended or continuous set of 'allowed' current waveforms. In comparison to the classical inverse class-F mode, this approach provides a much wider design space for the realization of broadband power amplifiers, where output performance can be maintained through the proper termination of harmonic current components over bandwidth. By varying simultaneously the susceptance of fundamental and second harmonic terminations, it will be shown how drain efficiency and output power can be maintained at constant high levels over significant bandwidth. For the validation of this new theory, measurements have been carried out on GaAs pHEMT transistor at 0.9GHz and at a drain voltage of 4V.