Concurrent multi-band power amplifier employing multi-section impedance transformer

This paper presents a novel concurrent multi-band power amplifier. A newly proposed multi-section impedance transformer provides impedance matching in individual bands at the same time. Each section is synthesized to match the corresponding operation band and to prevent impedance deviation in other matched bands by employing a branched stub. A 1W-class triple-band PA following the proposed scheme achieves a maximum power added efficiency of greater than 55% with a high output power of greater than 30 dBm at 0.9 GHz, 1.8 GHz, and 2.1 GHz.