Simulating complex power-ground plane shapes with variable-size cell SPICE grids

Power and ground planes can be simulated with rectangular uniform SPICE grids, or by analytically evaluating the double series of modal resonances. For nonrectangular shapes, the Transmission Matrix Method (TLM) can be used. For odd shapes, irregular outlines, cutouts and perforations, a variable-size cell grid is shown to be effective and sufficiently accurate. The adaptive grid preserves the static capacitance of the planes, calculates the modal resonances accurately in the presence of cutouts, and can also account for the perforations of planes.