Design of a broadband high-efficiency class-GF power amplifier using a two-stage branch line directional coupler

This paper proposes an extended technique to design broadband high-efficiency power amplifiers (PAs), in which the proposed extended design strategy integrates the theory of extended continuous mode PAs with an innovative approach for implementing circuits that meet the required theoretical impedances. The method uses impedance frequency modulation and is implemented by a two-stage branch line directional coupler with adjustable terminals. To illustrate the design procedure, a broadband high-efficiency PA operating in 0.7-3.0 GHz is designed and then fabricated by using a CGH40010F transistor. The test results show that the PA achieves an output power ranging from 40.1 to 42.8 dBm and a drain efficiency (DE) ranging from 60.8% to 75.0%. Additionally, the gain ranges from 10.1 to 12.5 dB within the target band. The realized PA exhibits an extremely competitive relative bandwidth of 124.3%.