Exactly solvable model for transmission line with artificial dispersion

Journal of Applied Physics. 2020. Vol. 128. Article 024901.

Shvartsburg A. B., Artekha S. N., N.S. Artekha

The problem of the emergence of wave dispersion due to the heterogeneity of a transmission line is considered. An exactly solvable model helps us to better understand the physical process of a signal passing through a non-uniform section of the line and to compare the exact solution and solutions obtained using various approximate methods. Based on the transition to new variables, the developed approach made it possible to construct exact analytical solutions of telegraph equations with a continuous distribution of parameters, which depend on the coordinates. The flexibility of the discussed model is due to the presence of a number of free parameters, including two geometric factors characterizing the lengths of inhomogeneities in values of the inductance L and of the capacitance C. In the new variables, the spatiotemporal structure of the solutions is described using sine waves and elementary functions, and the dispersion is determined by the formulas of the waveguide type. The dispersive waveguide-like structure is characterized by the refractive index N and the cutoff frequency Ω. The exact expressions for the complex reflection and transmission coefficients are derived. These expressions describe phase shifts for reflected and transmitted waves. The following interesting cases are analyzed: the passage of waves without phase change, the reflectionless passage of waves, and the passage of signals through a sequence of non-uniform sections. The developed mathematical formalism can be useful for the analysis of a wider range of problems. 

Keywords: wave propagation, Dispersion, transmission line model, Electrical properties