Supply Modulation Behavior of a Doherty Power Amplifier

Abstract

This paper presents a study of supply modulation in a Doherty power amplifier (DPA). To validate a simplified theoretical model, a 3.5 GHz conventional symmetrical DPA using a 6-W packaged GaN pHEMT is designed for supply modulation of the main and/or auxiliary amplifiers. The DPA is characterized in CW operation over a range of supply voltages, and shows up to 15 percentage point efficiency improvement at 12 dB output back-off when both main and auxiliary amplifiers are varied simultaneously. A comparison of three cases of supply variation is shown and potential benefits for improving back-off efficiency are discussed.

Keywords

• Doherty PA
• gallium nitride (GaN)
• load modulation
• power amplifier (PA)
• supply modulation