Inverse class-FJ: Experimental validation of a new PA voltage waveform family

This paper presents for the first time an experimental validation of the continuous inverse class-F mode with varying the voltage waveforms, also known as inverse class-FJ. Starting from the standard inverse class-F condition and varying fundamental and third harmonic impedances whilst maintaining an open-circuit second harmonic load it will be demonstrated that output power and drain efficiency can be maintained at near constant values. For the validation of the approach, experimental measurements have been conducted on-wafer on a GaAs pHEMT device operating at 4 V supply voltage and 0.9 GHz fundamental frequency. The experimental results show that output power of 19.3-19.6 dBm and drain efficiency of 75-80% can be maintained for different sets of fundamental and third harmonic impedance solutions, which can then be translated in a useful design space for designing broadband power amplifiers.