Analysis of Nonuniform Transmission Lines With a Perturbation Technique in Time Domain

This paper presents an iterative perturbation technique for the time-domain analysis of nonuniform transmission lines. Compared with the mostly reported frequency-domain methods, the time-domain method possesses the advantages of efficient computation and intuitive observation of computed results. For the consideration of nonuniformity, the place-dependent variation of the per-unit-length parameters is interpreted as perturbations relative to uniform transmission lines. The nonuniform transmission lines can thus be regarded as the superposition of the unperturbed part and the perturbed part. Starting from the Telegraph's equation, the time-domain expression of the proposed method is derived. Then, multisteps consecutive perturbations based on the finite-difference time-domain method are formulated to analyze the field-line coupling problem. As the perturbation order increases, the perturbation value converges rapidly to a certain value. The technique is validated through the analysis of an overhead multi-conductor nonuniform transmission lines. The high efficiency of the proposed method in solving the electromagnetic compatibility problem with randomicity is verified and applied by analyzing a nonuniform transmission line with randomly varying paths.