Finite Element Extraction of Frequency-Dependent Parasitics

We propose a stable and efficient approach to extract the frequency-dependent parasitic effects of any computer-aided design (CAD) model with the finite element method (FEM). An equivalent circuit (EC) of the parasitics for use in transient circuit simulations is generated by applying vector fitting to the result of a full-wave simulation on the one hand and to a magnetoquasistatic (MQS) simulation result on the other hand. The circuit generated from the magnetoquasistatic results is combined with capacitances computed in an electrostatic (ES) simulation. This separate consideration of resistive and inductive, and capacitive effects ensures stability also at low frequencies by avoiding impedance or scattering matrices that otherwise would become ill-conditioned when approaching the dc point. A comparison of measurement and simulation results for the example of a common mode (CM) choke validates the method.