A new approach is presented for modeling the resistances of the substrate coupling network employed for noise calculations in the design of mixed-signal and RF ICs. The approach introduces intermediate resistances having progressively simpler current flow patterns than the coupling resistances. Each coupling resistance is then modeled as the product of two resistance ratios and a resistance having simple 1-D vertical or lateral flow, and each resistance ratio is approximated as a simple function of geometrical aspect ratios. Based on this approach, closed-form expressions are derived for coupling resistances associated with parallel stripe contacts on a substrate with or without a bottom contact, in terms of dimensions of the contact configuration and substrate parameters.