Transient Simulation Based on State Variables and Waves

This article reports a new method for transient analysis of nonlinear circuits based on nonlinear device state variables and waves at their ports. The method is based on relaxation and thus does not require large matrix decompositions if time step is constant. The use of waves results in guaranteed convergence for any linear passive circuit and some types of nonlinear circuits. Additionally, the formulation using waves ensures that nonlinear devices are always excited with a physically meaningful input, i.e., the amount of power transmitted to nonlinear devices is bounded. The method was implemented in the fREE-DA (TM) circuit simulator. The formulation, its properties, and a convergence analysis of the proposed method are presented first, followed by case studies. (C) 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE 21:314-324, 2011.