Class-F power amplifiers with reduced conduction angles

This paper determines the characteristics of class-F power amplifiers (PAs) with “class-C” conduction angles (current flow for less than half of the RF cycle). Analyses are conducted for both clipped-sinusoidal (classical class-C) and rectangular current waveforms. It is not possible to define the voltage and current waveforms arbitrarily if the production or sinking of power at the harmonic frequencies is to be avoided. As a result, only a few cases are of practical interest. In these cases, the conduction angle is set to null a specific harmonic in the current. The nulled harmonic is then used to flatten the bottom of the voltage waveform, resulting in increased efficiency and increased power output