Finite Difference Analysis of a Cylindrical Two Conductor Microstrip TransmissionLine with Truncated Dielectrics

摘要

The characteristics of the quasi-static TEM mode of a cylindrical microstriptransmission line are investigated using the finite difference technique. The transmission line consists of two perfectly conducting strips located between two different layers of dielectric materials, and a dielectric notch embedded in the substrate between two strips. The dielectric overlay and substrate are truncated for practical purposes. The formulation of the problem is based on the solution of Laplace's equation subject to appropriate boundary conditions and the use of Taylor's expansion to approximate the first and the second order derivatives in Laplace's equation. To truncate the finite difference mesh, three different kinds of artificial boundaries have been considered. It has been found that an efficient solution is obtained when the artificial boundary is separated from the conducting core at a distance of the order of the height of the substrate. The goal of this research is to study the effects of the parameters of the multi-layered cylindrical transmission line on the odd and even mode phase velocities, and on the electrical coupling. Another objective of this study is to present several techniques to minimize the coupling between the two conductors. Once the odd and even mode phase velocities are equalized, the design of a distortionless line is achievable. The line capacitances are found to vary linearly with the dielectric constants of the overlay and the substrate. (AN).