A Wideband 100W Doherty Power Amplifier

Abstract

In this paper, design, fabrication and measurement results of a Doherty power amplifier (DPA) with a fractional bandwidth of wider than 90% is reported. An inverter-less architecture was used to overcome intrinsic bandwidth limitation of conventional DPAs. Instead of using a conventional narrowband quarter wavelength transmission line, by applying a post impedance matching network, the load impedance was converted to a lower impedance and then using a low order matching network, it was matched to the optimum load impedances of the transistor. Output matching networks of both the main and auxiliary amplifiers were designed with maximum efficiency in mind. In a frequency band of 650 MHz to 1750 MHz, measurement results of the fabricated DPA show an average saturated output power of around 100 Watts and a drain efficiency between 56%-78% and 49%-60% at saturation and 6dB back-off, respectively.