Formulation of the Singular Integral Equation Technique for Planar Transmission Lines

The singular integral equation technique is used to determine the normal modes of propagation in general planar transmission lines. Taking finlines as, an example, it is demonstrated how high-order modes can effectively and accurately be calculated. It is also shown that complex and backward-wave modes, which are known to exist in rectangular and circular waveguides with dielectric inserts, can also exist in finlines. Besides a discussion of their characteristic features, this paper describes the conditions under which complex and backward-wave modes are found in finlines.