A Simple Lumped-Element Topology for Wideband Class-E Operation at UHF and L Bands

In this paper, a lumped-element circuit topology is presented for approximating class-E operation along a wide frequency range. Exploiting the design space offered by the generalization or continuum of class-E equations, a dc-feed coil and a simple doubly resonant output network may provide the required terminating conditions for a high-efficiency and nearly constant output power amplifier operation over a significant fractional bandwidth. The topology is insensitive to resistive load variations at the central frequency, of potential interest for its use in load modulation (LM) transmitter architectures among other applications. Two GaN HEMT power amplifiers have been designed and characterized at UHF and L bands. The measured efficiency is above 75%, from 625 MHz to 1025 MHz and from 1.075 GHz to 1.375 GHz, respectively.