High-Efficiency VHF Polar and Doherty Amplifiers for Satellite Transponder Applications

New satellite VHF airband communication services are designed to provide aircraft communication with air traffic control (ATC) in remote and oceanic areas, leveraging existing airborne equipment and integrating seamlessly with current systems. Owing to the use of small satellites, the design of their power amplifiers (PA) presents a challenge in terms of power efficiency and linearity. This paper shows a polar power amplifier (PPA) and a Doherty power amplifier (DPA) designed for these new VHF satellites and compares their results. The PPA consists of a wideband Class-D RF high-efficiency power amplifier (HEPA) powered by a state-of-the-art performance hybrid envelope amplifier (HEA) based on GaN HEMT technology, whereas the DPA employs a broadband design that combines a Class-AB amplifier with a Class-C amplifier. Comparative measurements performed on prototypes of both systems show comparable performance in terms of efficiency and linearity for signals composed of four aggregated airband communication channels. Their efficiency is significantly higher than that of a Class-B amplifier, whose results are also shown.