A Stacked Doherty Power Amplifier For Ka-Band Space Applications

This paper presents the design and preliminary experimental characterization of a Monolithic Microwave Integrated Circuit (MMIC) Doherty Power Amplifier (DPA) conceived for satellite downlink Ka-band (17.3-20.3 GHz), manufactured in Gallium Nitride on Silicon (GaN-Si) High Electron Mobility Transistor technology with 0.1 mu m gate length available at OMMIC foundry. The DPA is based on a three-stage architecture in which the devices in the output stage of both Carrier and Peaking branches are implemented in a stacked configuration. The MMIC shows preliminary experimental results in agreement with the simulations achieving a small signal gain larger than 25 dB and input and output return losses better than 10 dB. Expected nonlinear performances show a saturation output power of 38 dBm, a gain better than 22 dB, and a Power-Added Efficiency of 37%, which remains higher than 25% at 6 dB of output power back-off.