 The FDFD equations can be rearranged in such a way as to describe a second order equivalent circuit, where nodal voltages represent the E field components and branch currents represent the H field components.This equivalent circuit representation can be extremely useful, as techniques from circuit theory can be used to analyze or simplify the problem and can be used as a spice-like tool for three-dimensional electromagnetic simulation.This susceptance element equivalent circuit (SEEC) model has the advantages of a reduced number of unknowns, only having to solve for E field components, and second order model order reduction techniques can be employed.