Evaluation of characteristic impedance of twin-wire transmission line insulated by multilayer dielectric

A method is presented of finding the characteristic impedance of twin-cylinder transmission line, each of which is covered by multilayer dielectric based on conformal transformation. Cotangent hyperbolic transformation is used to transform the cross-sections of the metallic boundaries to parallel plates and dielectric boundaries to curved contours. The curved contours are replaced by a large number of discrete steps and the capacitance per unit length of the structure is found from a series and parallel combination of infinitesimal capacitances. The characteristic impedance is found from the capacitance per unit length. Numerical results on capacitance per unit length and characteristic impedance are presented. © 1997 Taylor and Francis Group, LLC.