The influence of test method, conductor profile and substrate anisotropy on the permittivity values required for accurate modeling of high frequency planar circuits

Abstract

Purpose

The purpose of this paper is to help high frequency circuit designers understand how to choose the best permittivity value for a laminate material for accurate modeling.

Design/methodology/approach

In this paper, experimental measurements of the performance of simple circuits are compared to various mathematical and software models.

Findings

Higher permittivity values were obtained using samples with bonded copper foil compared to samples etched free of foil. These higher values yielded better agreement between measured and modelled performance using current automated design software. High profile foil on thin laminates was found to increase the surface impedance of the conductor and change the propagation constant and apparent permittivity of the laminate by 15 percent or more. It was also demonstrated that, under some circumstances, the anisotropy of the substrate could result in differences in measured and modelled performance.

Research limitations/implications

Only a limited number of circuit laminate materials were closely examined. Future work should include a wider variety of laminates.

Originality/value

The paper details the magnitude of the effects of test method, conductor profile and substrate anisotropy on the values of a material's permittivity best suited for circuit design purposes.

Citation

Horn, A.F., LaFrance, P.A., Reynolds, J.W. and Coonrod, J. (2012), "The influence of test method, conductor profile and substrate anisotropy on the permittivity values required for accurate modeling of high frequency planar circuits", Circuit World, Vol. 38 No. 4, pp. 219-231. https://doi.org/10.1108/03056121211280431