Class B* - A New High Efficiency RF DC/DC Converter Concept Using Second Harmonic Generation/Injection

RF DC/DC converters typically treat power amplifier and rectifier separately. This paper presents a novel approach to designing converters based on the interaction between amplifier and rectifier. By utilising the second harmonic power generated in the rectifier to realise second harmonic injection to the power amplifier, both can be operated at high efficiency. This waveform engineering based concept is explored mathematically and then simulated. Based on this analysis, a class $\mathrm{B}^{*}$ rectifier based on a 0.25 $\mu \mathrm{m}6\mathrm{x}80\mu \mathrm{m}\mathrm{G}\mathrm{a}\mathrm{N}$ HEMT is measured using a load-pull/source-pull measurement system to emulate the required harmonic impedance environment. The resulting voltage and current waveforms are de-embedded to the intrinsic current generator plane and analysed, confirming the ability of this kind of rectifier to provide beneficial second harmonic injection to a power amplifier. The rectifier‘s efficiency is measured to be more than 90% over an input power range of 20 dB if the generated second harmonic is taken into account.