High-Efficiency Class-E-1 and Class-F/E Power Amplifiers at Any Duty Ratio

In this paper, the Class-F-n/E power amplifier (PA) and the inverse Class-E (Class-E-1) PA under zero-current switching and zero-current-derivative switching conditions at any duty ratio are analyzed. The maximum switch voltage and current, output power capability, and element values as functions of the duty ratio are obtained for both classes. The main objective of the analysis is to choose the proper duty ratio to maximize the output power capabilities at optimum conditions. The element values are dependent upon the duty ratio and require a careful selection of the duty ratio to reach desired specification. The effect of the duty ratio D = 0.3-0.7 on the performance of the Class-E-1 and Class-F-3/E PAs is demonstrated. The duty ratio is used not only as the design specification but also as the adjusting parameter for achieving a certain condition. The measured maximum drain efficiency of 88% and 87% are obtained at 4 MHz at 30-dBm input power for the Class-F-3/E and Class-E-1 PAs, respectively. The results show that lower peak switch voltage and current are obtained in the Class-F-3/E PA in comparison with Class-E-1 for the same conditions.