Closed-form expressions for the current distributions on open microstrip lines

The authors systematically clarify the characteristics of current distributions for various cases of substrate relative permittivity, shape ratio, and normalized frequency. These characteristics are clarified, and closed-form expressions are proposed. An open microstrip line with isotropic dielectric substrate is numerically analyzed by the spectral-domain method to clarify current distributions on a strip conductor. The current distributions obtained are illustrated in figures for typical cases. A full view of current distributions on a strip conductor in any microstrip line is provided by showing those close-form expressions. These expressions for the current distribution have been compared with the theoretical results, and good agreement has been obtained