In this paper, we reformulate the quasi-static spectral-domain approach, using the partial capacitance method (PCM), to compute the w/h and s/h dependent equivalent isotropic substrates corresponding to the anisotropic substrate asymmetric coplanar waveguide (ACPW), coplanar waveguide (CPW), micro-coplanar strip line (MCS), and microstrip line. We have used the closed-form dispersion relations over equivalent substrates to obtain the dispersion in these line structures. For this purpose, the ACPW and MCS structures are converted to the equivalent symmetrical CPW and the available closed-form dispersion model for the CPW is adapted to the ACPW and MCS structures. The dispersion results for these lines are compared against the results of the HFSS with average deviations in the range of 1%–4%. We get nearly the same range of deviations in the results of HFSS against the experimental results on the isotropic substrates.