The measured performance shows excellent agreement with the design calculations. The results can be used for designing Class E stages at any Q and switch duty cycle D. For example, for Q at D = 0.5, some errors are up to 60 percent. Therefore, the high- Q assumption used in previous analyses leads to considerable errors. It is shown that all parameters of the amplifier are functions of Q. The following performance parameters are determined for optimum operation: the current and voltage waveforms, the peak collector current and collector-emitter voltage, the output power, the power-output capability, the load-network component values, and the spectrum of the output voltage. The basic equations governing the amplifier operation are derived analytically using Laplace-transform techniques and assuming a constant current through the dc-fed choke. This paper presents an exact analysis of the Class E amplifier at any Q and any switch duty cycle D, along with experimental results. Power-output capability increases by up to 27%.read more read lessĪbstract: Previous analytical descriptions of a Class E high-efficiency switching-mode tuned power amplifier have been based on the assumption of an infinite Q or the minimum possible value of Q. Efficiency increases from 50% of class A toward 100% as harmonics are added. Amplifier performance is then tabulated as a function of which harmonics are included in the voltage and current waveforms. Fourier coefficients for maximally flat waveforms are then derived for inclusion of up to the fifth harmonic. This note first derives the basic relationships among the Fourier coefficients of the waveforms and the performance of the amplifier. However it is possible to control the impedances at a finite number of harmonics. At VHF and higher frequencies, the drain capacitance, lead inductance, lead length, and dispersion make implementation of reasonably ideal tuned circuits difficult. Generally, the output network must present the drain with either an open or short circuit at the harmonic frequencies. Abstract: Class-F power amplifiers (PA's) employ harmonic-frequency resonators to shape their drain or collector waveforms to improve efficiency.
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March 2023
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