Transmission-line compensation circuit of parallel-circuit class-E power amplifier to extend maximum operating frequency

Presented is a modified parallel-circuit class-E amplifier that operates above the theoretical maximum frequency, recovering the class-E operating conditions. The finite inductor in the parallel circuit topology is replaced by a more suitable network composed of four transmission lines. The theory formula of the circuit elements of the proposed network is derived in detail, and an example is designed and measured to validate the analysis. The measured maximum output power of 40 dBm, drain efficiency of 77.5%, and power-added efficiency of 70.8% at 2.8 GHz were obtained, showing excellent efficiency compared to that obtained by other amplifiers using the same device.