An efficient microwave outphasing transmitter based on class-E power amplifiers

Abstract

This article presents two alternative topologies combining lumped and distributed elements for designing class-E power amplifiers (PAs) for the 3.5 GHz frequency band, that differ in their approach to terminating the second harmonic. The first design employs a transmission line with a capacitor to create a short-circuit, while the second design uses a simple stub. The first design outperforms the second one in terms of efficiency enhancement. Accordingly, an outphasing transmitter based on a surface mount hybrid coupler combiner is designed using the first topology, achieving peak value results of 78% drain efficiency and 44.3 dBm output power. At a 6 dB back-off point, the simulation results show that the proposed architecture achieves 67.6% drain efficiency.