Modified spectral-domain approach for microstrip lines with finite metallisation thickness and conductivity

A modified spectral-domain approach is proposed for an analysis of the microstrip line whose signal strip and ground plane have finite thickness and conductivity. To improve the accuracy of the results, all three components of the strip current which have three-dimensional dependence are included in the analysis. With the basis functions properly chosen, this new approach can be treated as easily as the conventional spectral-domain approach. By this modified approach, both the phase constant and attenuation constant can be determined simultaneously without using the assumption that the skin depth is much larger or smaller than the signal strip thickness. In this work, comparison with published theoretical and experimental results is presented to check the accuracy of the new approach. In particular, the effective dielectric constant and attenuation constant of a microstrip line with finite metallisation thickness and finite conductivity are discussed in detail, together with the longitudinal current distributions along the signal strip.