EFFECT OF SECOND AND THIRD HARMONIC INPUT IMPEDANCES IN A CLASS-F AMPLIFIER

Abstract

In this paper, the design of a class-F radio frequency power amplifler with a multiharmonic input transmission line network is presented. Harmonic signal components at the gate come from several sources including nonlinear device capacitances and imperfect output harmonic terminations that create harmonic components that are fed back to the gate through the gate-drain capacitance. The efiect of these harmonic generation mechanisms and the potential to shape the gate waveform to improve power e-ciency are investigated. The study shows that a second harmonic short is most beneflcial and the efiect of a third harmonic termination is less signiflcant. The concepts are applied to the design of a 10W GaN class-F amplifler and the design is supported by theoretical, simulation and experimental results. The fabricated design has a measured drain e-ciency of 78.8% at an output power of 40.5dBm for a frequency of 990MHz. The amplifler was also tested with a 8.8dB peak-to-average power ratio 5MHz WCDMA signal. With the modulated signal, the adjacent channel power ratio was i33:1dBc at a drain e-ciency of 46.1% without predistortion correction.