The class E/F family of harmonic-tuned switching power amplifiers

A new family of harmonic-tuned switching amplifiers is introduced having the beneficial features of the class-E tuning while allowing improved performance to be achieved through additional harmonic tuning. This E/F family may be tuned to achieve the ZVS/ZdVS switching features characteristic of the class-E amplifier and, like the class-E tuning, accounts and compensates for the effect of the switch parallel capacitance. By tuning one or more overtones to the class-F−1 tuning, however, the switching waveforms may be improved, lowering the peak voltage and reducing the RMS current. Additionally, the tolerance to large switch parallel capacitance is generally improved so that a larger switching device may be used, allowing reduction of the on-resistance. Due to these factors, the efficiency of E/F amplifiers is expected to exceed that of class E.; To demonstrate these advantages, methods of estimating the optimal efficiency of switching amplifiers using waveform properties are given. A general solution technique is then presented which allows the calculation of the ZVS tuning requirements and the resulting switching waveforms for an arbitrary harmonic tuning. Using these two tools, switching waveforms and resulting efficiency estimates are calculated for E/F amplifier tunings, which are then compared to class E.; Finally, potential application areas of the E/F technique are explored, and measured results of several first-generation E/F amplifiers are presented. Aside from efficiency benefits, E/F amplifiers also may achieve load-invariance, dual- and multi-band operation, high volumetric power densities, and efficient integrated circuit implementation using the Aoki distributed active transformer power combining structure.