Development strategy for GaN-based high-efficiency hybrid medium-power RF amplifiers through low-cost substrate prototyping

Two high-efficiency power amplifiers have been designed, fabricated, and tested using a commercially available GaN HEMT transistor and a low-cost hybrid microstrip PCB. The designed hybrid modules are a “tuned load” Class B amplifier and a Class F amplifier. The simulated performances show a peak efficiency of 72 and 78% with an output power of 5 and 4.5W respectively. The measured performance, although still satisfactory, exhibits an efficiency of 60 and 55%, respectively, for the two stages. The paper presents a discussion on the design approach, on the intrinsic/extrinsic load to be presented to the active device, and on the cause of the efficiency drop occurring between the simulated and measurement performances.