Ku-band, 120-W power amplifier using gallium nitride FETs

In this paper, we present a 120-W solid-state power amplifier (SSPA) for Ku-band applications. At the final stage of the SSPA, eight gallium nitride (GaN) field effect transistors (FETs) are combined. A suspended line type of combiner is designed using a three-dimensional electromagnetic (3D-EM) simulator so that the combiner can have a good performance in terms of insertion loss. To improve the linearity of the SSPA, we apply a linearization technique to the study of GaN FETs at the driver and final stages in the SSPA. Measurement results show a third-order intermodulation distortion (IM3) of -32 dBc and a power efficiency of 9% at an output power of 120 W at frequencies of 14.0 GHz to 14.5 GHz. This is the first report on a Ku-band SSPA with higher output powers than 100 W using GaN FETs.