Class-E PA efficiency enhancement using zero voltage switching contour control

In this paper, we present a review of recently proposed zero-voltage-switching (ZVS) contour power amplifier (PA) architectures based on simultaneous duty-cycle modulation and load modulation. Fundamental principles to enhance power efficiency at back-off region are explained on the basis of class-E PA and their operations are verified using series/parallel versions of implementation. Outstanding issues with ZVS contour PA control are briefly discussed.