The spectral-domain method is used to compute the effective dielectric constant ( epsilon /sub r///sub eff/(f)) of open and shielded microstrip lines to analyze the dispersion distortion of short electrical pulses. Precise expressions for the longitudinal and transverse current distributions allow a high level of accuracy for epsilon /sub r///sub eff/(f). It is determined that computation time can be minimized for the open microstrip calculations by using the shielded microstrip formulation provided large dimensions for the conducting walls are assumed. >