A 100-W Doherty Power Amplifier With Super-Octave Bandwidth

Abstract

This brief presents design, fabrication, and measurement results of a high-power Doherty power amplifier (DPA) with a fractional bandwidth of wider than 90%. An inverter-less architecture was used to overcome the intrinsic bandwidth limitation of conventional DPA in which a quarter wavelength impedance inverter is utilized. Thanks to the use of a real-to-real post impedance matching network, the modulated impedance at the load modulation point was simply [using simple output matching networks (OMNs)] transferred to the optimum load impedances of the transistors which of course dynamically change with changing the output power. Input and OMNs of both the main and auxiliary amplifiers were designed with maximum efficiency in mind not only in saturation but also in an output back-off region. In a frequency band of 650–1750 MHz, our measurements showed an average saturated output power of 100 watts and a drain efficiency between 56%–78% and 41%–61% at saturation and 6-dB back-off, respectively. Compared to the state-of-the-art broadband high-power DPAs, the one presented in this brief is shown to provide the highest output power in the widest fractional frequency bandwidth while keeping the efficiency at a very high level in both the peak and back-off outputs.