Quasi-static characteristic of a shielded cylindrical coupled microstrip transmission line by finite-element method

This paper presents a finite-element method of numerical analysis for a system of a shielded cylindrical coupled microstrip transmission lines. The complete polynomial field of the high order element up to fourth is used in this study. The microstrip line consists of two coupled dielectric circular cylinders characterized by permittivity ε₁ and ε₂ and partially embedded in the ground plane. The two infinitesimally thin strips with arbitrary size are clad on the coupled dielectric circular cylinders. The coupling between the two conducting strips of the coupled microstrip line is investigated. The first and higher order elements are used in the finite-element method to calculate for the quasi-static potential and the corresponding field distribution in the microstrip line. The capacitance per unit length of the line is obtained from a variational expression and the effective dielectric constant, characteristic impedance, and phase velocity are also computed. A perturbational method is used to calculate the losses due to conductor and dielectric dissipation