Simultaneous load-pull and real-time infrared thermal imaging of RF/microwave power transistors

Thermal characterization and optimization of RF and MW power transistors represents a significant challenge to maximize effective power density and minimize thermal memory and its impact on linearity We describe a novel loadpull system with an integrated infrared thermal imaging system that allows real-time observation of steady-state die temperature versus source/load impedance. Spatial resolution of 2 μm allows examination of individual emitter fingers for HBT technologies, while the 2x2 mm field of vision allows examination of an entire die. The system is capable of presenting contours of spatial instantaneous temperature, spatial average temperature, and associating source/load impedance points with images representing full-color isotherms. Thermal measurements of an HJFET are shown to illustrate the capability of the new system.