An Extended Topology of Parallel-Circuit Class-E Power Amplifier to Account for Larger Output Capacitances

This paper presents a modified parallel-circuit class-E amplifier that accommodates devices with larger output capacitances, recovering the class-E operating conditions. The finite inductor in the parallel circuit topology is replaced by a more suitable network composed of a series inductor and additional subharmonic resonators. Analysis of the class-E amplifier allows to determine the required frequency-domain response of this new network. Derivation of the circuit elements of the proposed network is shown in detail, and a design procedure for this modified class-E is provided. The analysis is validated by simulation and design of a test board. Measurements of the test board showed a drain efficiency of 80.7%, power-added efficiency of 78.6%, and output power of 4.91 W at 434 MHz, exhibiting levels of efficiency similar to that obtained by other amplifiers using the same device, but at much lower frequencies. According to the authors´ knowledge, this study represents the first systematic approach to design class-E power amplifiers at UHF using devices with larger C_OUT by taking into account the use of arbitrary finite-feed class-E topologies.