Class-E, Class-C, and Class-F power amplifiers based upon a finite number of harmonics

TLDR

Class‑E operation at UHF and microwave frequencies is achieved by using transmission‑line networks to provide the drain harmonic impedances of an ideal class‑E power amplifier. This paper develops a technique for analyzing such amplifiers based on a finite number of harmonics. The technique is generally applicable to classes E, C, and F, and to PAs with non‑standard harmonic reactances. The analysis reveals that maximum efficiency is determined by the number of harmonics rather than the class, can be achieved for any harmonic set by adjusting waveforms and load reactance, and that power‑output capability is highest for class F.

Abstract

Class-E operation at UHF and microwave frequencies is achieved by using transmission-line networks to provide the drain harmonic impedances of an ideal class-E power amplifier (PA). This paper develops a technique for analysis of such amplifiers that are based upon a finite number of harmonics. The technique is generally applicable to classes E, C, and F as well as PAs with harmonic reactances not corresponding to those of established classes. The analysis shows that the maximum achievable efficiency depends not upon the class of operation, but upon the number of harmonics employed. For any set of harmonic reactances, the same maximum efficiency can be achieved by proper adjustment of the waveforms and the fundamental-frequency load reactance. The power-output capability depends upon the harmonic reactances and is maximum for class F.