AC resistance of two coupled strip conductors

In many modern planar microwave integrated circuits, structures involving coupled rectangular shape strips with the metallisation thickness comparable to the skin depth are encountered. This paper develops a formally exact method of analysis for the AC resistance based on the current distribution of this kind of structure. The method gives solutions for the electric field distribution inside and outside the strips. The separation of variables technique is used for the internal field distribution and the Green´s function technique is employed in finding the external field. The method is implemented numerically for the case of two adjacent coupled strips. It is found that by increasing the coupling of the lines, i.e. decreasing their separation, the AC resistance of each strip increases substantially. Moreover, the increase in AC resistance of odd coupled strips is significantly higher than that of even coupled strips. The result is shown to be consistent with the existing literature.