High efficiency switch mode GaN-based power amplifiers for P-band aerospace applications

Switch mode operation of a GaN HEMT device is explored to determine the performance and limitations of this technology for P-Band Pulsed waveforms. A combination of Class E and Inverse Class F amplifier operation is used to achieve high efficiency amplification. The measurements are based on a single 24mm GaN on SiC HEMT die operated at 50V bias, made by Integra Technologies, Inc. Harmonic tuning circuit techniques result in drain efficiency of 80%, and saturated power greater than 150W. The pulsed RF waveform used for this work has a pulse duration of 300uS and a 10% duty cycle. The operating frequencies at P-band are 420MHz to 450MHz. Measurements include bias modulation and drain sequencing circuit effects on amplifier efficiency. The presented results are part of an SBIR award from Jet Propulsion Laboratory / NASA, with the objective of designing and building a 1kW output power amplifier with greater than 80% efficiency for space exploration. To further facilitate the scaling of the presented techniques to a single ended part with 500W output power, we also present an investigation of a GaN on SiC transistor design to be operated at 100V bias at P-Band. The authors believe that the innovative approach discussed and proposed unleashes a new solution to the design of very high efficiency RADAR amplifiers for aerospace applications.