Full-Wave Electromagnetic Modelling from DC to GHz using FEM-SPICE

A full-wave FEM-SPICE technique is presented for modelling electromagnetic fields from DC to GHz. Previous implementations of this method have not worked well at low frequencies, because the circuit models generated from the finite element formulation had low-frequency stability problems. A modified LU recombination method is here applied to the standard FEM-SPICE formulation in order to eliminate the low frequency stability problem while allowing a reduction of the number of circuit elements. The equivalent circuit derived from the reformulated equations is suitable for analysis in the time and/or frequency domains by any circuit solver that can model large numbers of linear or non-linear lumped elements. Examples are provided that demonstrate the ability of the new technique to model geometries from DC to several GHz in a single simulation.