Power supply for a radio transmitter with modulated supply voltage

RF power amplifiers can save energy if the supply voltage is modulated dynamically. The power supply requires a low output capacitance to obtain a fast voltage modulation at very high efficiency and small size. These requirements become a challenge if a very good regulation under aggressive load current variations is also required. In this paper, a detailed analysis of the filter design and control of the Buck converter leads to a very high efficiency, small size design that meets dynamic regulation requirements, even aggressive load current variations, with low output capacitance. Interleaving of Buck converters proves to be the enabling solution. A prototype has been built and the measurements agree with the theoretical results.