Characteristic impedance of a microstrip line with a dielectric overlay

Abstract

Purpose

The purpose of this paper is to present an analytical expression for the characteristic impedance of a microstrip line in presence of a dielectric cover.

Design/methodology/approach

Assuming a quasi-TEM propagation mode, a rigorous conformal mapping based on the Schwarz-Christoffel transformation is employed to derive the equivalent capacitance model, which can then be applied to derive a closed analytical expression for the effective permittivity and the characteristic impedance of the line.

Findings

Such a formulation is not limited to the case of a single cover layer, but an arbitrary number of electric overlays can be considered as well. Comparisons with published numerical results and full-wave simulations in the case of a single cover layer have been also performed to test the validity of the proposed approach.

Originality/value

The new analytical formula for the characteristic impedance of a microstrip line with a single dielectric cover shows better performances compared to the one of closed formulas already presented in the literature.

Citation

Barbuto, M., Alù, A., Bilotti, F., Toscano, A. and Vegni, L. (2013), "Characteristic impedance of a microstrip line with a dielectric overlay", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 32 No. 6, pp. 1855-1867. https://doi.org/10.1108/COMPEL-10-2012-0283