The conventional analysis of waveguide parameters for microstrip components using the finite-difference time-domain (FDTD) method is based on monitoring the traveling wave at multiple locations. The dispersion relations of the effective dielectric constant and the characteristic impedance usually exhibit oscillatory behavior. An equivalent circuit approach was utilized for these parameters. Together with the FDTD results, the inductance and the capacitance were evaluated. The phase velocity and the characteristics impedance mere then calculated at a single monitor location. With this method, the oscillatory features in the dispersion relations were minimized.