A power amplifier by using asymmetrical branch-line coupler

In this paper, a novel power amplifier (PA) is proposed. An asymmetrical branch-line coupler is exploited as the output matching circuits of the proposed PA. Meanwhile, by setting the impedance conditions with trade-off in desired pass-band appropriately, impedance matching and output power combination can be realized in a single circuit. A brief analysis of the asymmetrical branch-line coupler is presented. Compared with the traditional high-power PAs design method, this design method can meet the requirement of the miniaturization. To prove the validity of the proposed method, a PA works at 2 GHz is designed, fabricated and measured by using a 10-Wgallium nitride (GaN) transistor (CGH40010F). The measured results show that a saturated output power of 42.8-45.2 dBm with a power-added efficiency of 52.0-62.6% is achieved and a saturated power gain between 7.9 and 10.1 dB.