Improvement of class E tube power amplifiers efficiency using new principles of grid voltages shaping

Abstract

The paper covers the ways of improving the efficiency of a tube Class E power amplifiers (PA) used in the output stage of high-power radio transmitters. Shifting PA in class E mode enabled to achieve anode efficiency of 88…93%. At the same time it led to a result that control and screen grid dissipated power in tetrode became one of the main factors hindering further improvement of PA characteristics. This problem can be solved by applying to the control and screen grids multilevel voltage with a certain parameters. It enables to increase either the anode efficiency or the output power. The examples of suggested grid voltage shapes and related to them PA characteristics are provided.