Analysis of coupled exponential microstrip lines by means of a multi-step perturbation technique

In this contribution, an iterative and adaptive multi-step perturbation technique for nonuniform transmission lines is presented and applied to the analysis of coupled exponential lines. The Telegrapher's equations for nonuniform lines, which do not have a closed-form solution, are recast as the equations for uniform lines with equivalent distributed sources, for which a well-known numerical solution procedure exists. The line voltages and currents are computed in multiple steps by iteratively updating the distributed sources. The method turns out to be faster than classical solutions based on the discretization of the line into uniform subsections. Two validation examples are proposed that deal with coupled exponential lines, which have relevant applicability in microwave components.