Source/load-pull characterisation of GaN on Si HEMTs with data analysis targeting doherty design

This paper presents the source/load-pull characterisation of GaN HEMTs on Si substrate, with an analysis of the measurement data oriented to aid the design of Doherty power amplifiers for satellite communication applications in the 17–20 GHz band. In particular, fundamental load-pull, in both class AB and C, is used to identify the output power and efficiency contours and assess the scalability of the performance vs. device size. Second harmonic source/load-pull data is used to determine the harmonic impedance regions to avoid during matching network synthesis. The load-pull data allows to predict the optimum load modulation trajectory to be synthesised in the design phase and the associated performance in terms of efficiency, gain compression and phase distortion.