Efficient sensitivity and variability analysis of nonlinear microwave stages through concurrent TCAD and EM modeling

An accurate, yet computationally efficient, Computer Aided Design (CAD) framework is proposed for the concurrent variability analysis of the active and a passive part of an RF/microwave nonlinear stage. Both the active and passive part are modeled, fully retaining a link to their physical and technological parameters. This allows for a global assessment of the nonlinear stage sensitivity and variability due to process variations. The active device is first modeled through Technology CAD (TCAD); then, the model is implemented within an RF/microwave Electronic Design Automation (EDA) circuit simulator through X-parameters. The passive part is modeled by means of accurate electromagnetic (EM) simulations and then taken into account in the circuit simulator through parametrized S-parameters. The method is demonstrated by analyzing a deep class AB Power Amplifier (PA) at 12 GHz in GaAs FET technology. In particular, a Monte Carlo analysis of the output power variability around the nominal value of 26.4 dBm due to technological variations of both active device and output matching network is presented. The active device variability is shown to dominate over the passive structure one, even if up to 30% of the overall variance is due to the passive elements at intermediate input power levels.