w-l A New Definition of Characteristic Impedance

Existing two-dimensional definitions of characteristic imped-ance can result in a wide range of values for the characteristic impedance of a given transmission line in inhomogeneous me-dia. This paper suggests a three-dimensional definition, the “TEM Equivalent ” characteristic impedance, which is unique for any given transmission line geometry and is appropriate for use in circuit theory applications. Comparisons with two-di-mensional results and comparisons with measurements are pre-sented. The TEM equivalent characteristic impedance rdso shows a non-monotonic dispersion which is not seen in the usu-al two-dimensional definitions but is seen in experimentally