A new amplifier power combining scheme with optimum efficiency under variable outputs

This paper presents a new power combining scheme, which has either one or four amplifiers on depending upon the levels of input signal. This approach realized by utilizing a unique combiner that is lossless and has constant gain under both scenarios. As a result, for the system where variable output power is required, this combining scheme can be used in an amplifier design with optimum efficiency. Measurement data show 15% power efficiency for the four-amplifier scenario and 28% for the single amplifier scenario at 13dBm input power. We also investigate the possibility of using this combiner in an envelope tracking amplifier.