K-Band Doherty and Class AB Gallium Nitride MMIC Power Amplifiers for Space Applications

This paper compares the performance of Class AB and Doherty Gallium Nitride (GaN) Power Amplifier (PA) MMICs at 19GHz. The MMICs have been designed in the same process and fabricated on the same wafer to enable the ability for direct performance comparison. Measurements of the AM/AM and transfer curves, Linearity, and Power Added Efficiency have been made for each MMIC PA. Finally an assessment of these performance parameters with respect to output power backoff (OBO) will be presented to help normalize the comparison. To the authors knowledge this is the first time these power amplifier architectures have been compared at these frequencies (2). Additionally, to the best of the author's knowledge the performance for these amplifiers show state of the art PAE for GaN PA MMIC amplifiers at these frequencies.