Class E Power Amplifiers and Frequency Multipliers with Finite DC-Feed Inductance

Previous descriptions of class E amplifiers and frequency multipliers have required a radio frequency choke between the dc power supply and the active device “switch.” In this paper, it is shown that class E operation may be maintained with the RF choke replaced by a smaller reactance. The analysis technique used is similar to that used by Raab in his description of class E amplifiers in that the equations describing circuit operation are obtained from Fourier series methods and the assumption of an infinite output network Q. The equations so obtained are used to determine (1) optimum operation (maximum power output capability at 100-percent efficiency) at any harmonic and (2) design equations that yield the requisite component values for optimum operation. The equations show that class E circuits may be configured to accommodate devices with arbitrary output capacitance and that class E amplifiers may be configured to provide greater power output capability than can be obtained using an RF choke design. Class E circuits with moderate values of output network Q were constructed and tested. The measured performance of these experimental circuits shows excellent agreement with the theoretical performance predicted by the equations. © 1987 IEE