A MASH-Controlled Multilevel Power Converter for High-Efficiency RF Transmitters

Envelope tracking (ET) is one of the most promising transmitter architectures proposed to increase the efficiency of modern wireless communication system. An ET transmitter consists of a linear RF power amplifier and a high-efficiency envelope amplifier, which is always a switched-mode power converter. The envelope amplifier provides a varying drain (collector) bias voltage, which tracks the envelope of the RF input signal, for the RF power amplifier. Thus, the RF power amplifier keeps working in high-efficiency region of most of the time. Therefore, the overall efficiency of the transmitter is increased. This paper proposes a multistage noise-shaping-technique-controlled multilevel power converter to perform as the envelope amplifier in an ET transmitter. Experimental results show that the proposed power converter can reproduce any envelope signals with the maximum spectrum component of 300 kHz and give maximum instantaneous power of 20 W. Compared with pulsewidth modulation, the noise-shaping technique can shape the ripple into noise and the noise will be attenuated by the low-pass filter, which results a better performance, while maintaining high efficiency as well.