A systematic optimization strategy for microwave device modelling

The degree of ill-conditioning in the small-signal GaAs MESFET equivalent circuit model is formally quantified using a systematically formulated principal components sensitivity analysis procedure. With this procedure it is possible to estimate for the first time how reliable the component values are in the optimized model. On this basis the extraction of the MESFET equivalent circuit model is compared using electrical model components and physical model parameters. An optimization strategy which improves the condition number of the model so that rapid convergence and accurate models are ensured is presented. This technique transforms the axes of the model from the equivalent circuit components, which are correlated, to the uncorrelated principal component aces, which can be systematically scaled to eliminate ill-conditioning. Using this technique it is possible to obtain accurate estimates of the insensitive model parameters such as the parasitic resistances without resorting to direct measurement techniques