Accuracy considerations of power-ground plane models

Power and ground planes in high-speed printed-circuit board stack-ups must be considered as two-dimensional transmission lines. In circuit simulations, the analytical expression of the plane impedance provides an easy means to compute the impedance at any arbitrary location. The expression of impedance contains a double infinite summation of modal harmonics which in practical calculations must be truncated. This paper discusses the effect of truncation, and it is shown that the summation limits should be set according to the dimensions and loss characteristics of the power-distribution planes.