A multiple-input digitally controlled buck converter for envelope tracking applications in radiofrequency power amplifiers

Abstract

Wireless communication transmitters have very low efficiencies due to the use of linear radiofrequency power amplifiers. Several techniques have been proposed over the years to improve the efficiency of these systems. One of the most promising is called the envelope tracking technique, which is based on using a fast switching mode power supply to provide a varying voltage to the power amplifier that tracks the envelope of the transmitted signal. The amplifier can, thus, operate continuously near its theoretical maximum efficiency, greatly improving the overall efficiency of the communication system. This paper proposes a multilevel digitally controlled power supply suitable for this application. It is shown to perform very well, achieving very high efficiency, high-output power capability and tracking bandwidths above 50 kHz. This paper also shows that the proposed system is able to produce a 15% overall increase in efficiency in a complete envelope tracking system