Analysis and design of transmission-line structures by means of the geometric mean distance

This article describes the geometric mean distance (GMD), a tool for calculating the various direct-current inductances in any multi-conductor transmission line. Two examples of its use are given. For a two-conductor transmission line consisting of rectangular conductors, the GMD is calculated by means of integration and also by discretizing the conductors and treating them as composite conductors. The obtained values for the GMD is then used to calculate the inductance of each conductor. A two-conductor foil transmission line is also investigated and the GMD is used to determine the optimal foil shape for a given conductor inductance and minimum conduction losses. Finally, the advantages and limitations of the use of the GMD are discussed