The electro-thermal modeling of high power microwave FET and its applications

A complete electro-thermal model (E-T) for a high power microwave FET based on a nonlinear channel current equation and small signal extraction methodology combined with a solution of 3D thermal problem for an arbitrary pulsed thermal excitation in the area of transistor is presented. The temperature dependencies of the E-T model describing long-term as well as short-term thermal effects have been derived from solution of heat conducting equation (HCE) using 3D-FDTD thermal method and experimental results. This model is used to predict the performance of a high power amplifier (HPA) over a -35 degrees C to +60 degrees C temperature range in a wide frequency band for different operating class and modes (cw, pulsed and keyed bias). The E-T model was experimentally verified for designing L, S and C-band high power amplifiers with an output power level up to 200W using LDMOSFET's and MESFET's.