Equivalent circuit parameter extraction of microstrip coupling lines using FDTD method

A new algorithm, in conjunction with FDTD simulation, was developed to perform direct extractions of the equivalent circuit parameters for the coupled microstrip lines. The unit-length capacitance and inductance were derived from the FDTD results. The frequency-dependent microwave parameters such as phase velocity and the characteristic impedance do not show anomalous oscillation. Incorporated with the even-odd analysis, the scattering parameters of the coupled microstrip lines with a flexible coupling length can be calculated. The calculation results were found in good agreement with the measured scattering parameter data.