Two-phase buck converter as a dynamic power supply for RF power amplifier applications

In radio-frequency (RF) switched-mode tuned power amplifiers (PA), the RF amplitude at the output of PA is a direct and linear function of the supply voltage provided by voltage regulator module (VRM). This phenomenon has been utilized effectively in order to obtain high efficiency amplitude modulated power amplifiers. The presence of capacitor voltage ripple at the output of VRM adversely affects the modulation signal. Consequently, the signal at the output of PA may also suffer from distortion resulting in reduction in efficiency. In this paper, a two-phase buck converter is considered and the effect of ripple suppression is analyzed. The main advantage of the two-phase converter is that by changing the number of phases and hence, the duty cycle, amplitude modulation can be achieved with significant reduction in ripple and improvement in peak-to-average-power ratio. Further, the functionality of class-E power amplifier is presented in brief and used as a load to the VRM. Simulation results obtained using SABER circuit simulator are also presented and few concluding remarks are provided.