Simple and accurate dispersion expression for the effective dielectric constant of coplanar waveguides

A conformal mapping based analytic formula is proposed for computation of the frequency dependent effective dielectric constant, ɛeff, of coplanar waveguides (CPW). This formula is correct in a wide frequency band and for wide range of CPW parameters, and models both negative and positive slopes in the frequency dependence of ɛeff. The results are especially useful for modeling microwave/millimetrewave and ultrahigh speed digital interconnects