Closed-Form Expressions for the Current Densities on the Ground Planes of Asymmetric Stripline Structures

In this paper, closed-form expressions for the current density on the ground planes of an asymmetric stripline structure are derived. The derivation utilizes image theory in order to obtain a suitable quasi-static Green´s function for this asymmetric geometry. For the special case of a symmetric stripline geometry and the limiting case of a microstrip line, it is demonstrated that the results obtained here reduce to previously derived results. As expected, it is illustrated that the current densities on the ground planes of an arbitrary asymmetric stripline are bounded by the current distribution of a symmetric stripline and that of a microstrip line. The validity of the analytical results is investigated by comparing to numerically obtained results. Finally, expressions are presented for the total ground-plane currents as fractions of the total current on the signal trace