1. A method of modeling capacitance for a subject structure comprising a pair of long conductors surrounded by a dielectric material and supported by a substrate, wherein the capacitance of the conductors is a function of current frequency, wherein the method includes the steps of: assuming the surrounding dielectric material is a first dielectric with a first permittivity (ε 1 ) and the substrate is a second dielectric with a second permittivity (ε 2 ); determining the reflection coefficient for the subject structure and the basis structure based on the first and second permittivities (ε 1 , ε 2 ); determining the mirror capacitance for the basis structure; and computing the capacitance of the subject structure based on the reflection coefficients and the mirror capacitance.