Evolution of New Real and Complex Improper Solutions of the Slotline Dispersion Equation

An attempt is made in this paper to reach a better understanding of the behaviour of open uniplanar circuits, particularly the slotline. A new second leaky wave has been revealed in addition to the dominant bound and leaky waves known up to now. The evolution of its dispersion characteristics in dependence on the line dimensions is presented. Possible excitation of this new leaky wave brings down the upper cut-off frequency of pure bound wave propagation. Consequently the new leaky wave associated with simultaneous leakage into two surface waves can significantly deteriorate circuit performance, especially in the mm-wave band. Conclusions achieved for the slotline can be extended qualitatively to the other printed-circuit lines.