Title page for ETD etd-10102005-131557


Type of Document Dissertation
Author Andrawis, Madeleine Y.
URN etd-10102005-131557
Title Dielectric loss determination using perturbation
Degree PhD
Department Electrical Engineering
Advisory Committee
Advisor Name Title
Davis, William A. Committee Co-Chair
Riad, Sedki Mohamed Committee Co-Chair
Besieris, Ioannis M. Committee Member
Brown, Gary S. Committee Member
Elshabini-Riad, Aicha A. Committee Member
Kohler, Werner E. Committee Member
Keywords
  • Cavity resonators
  • Convergence
  • Perturbation (Mathematics)
  • Dielectric loss
Date of Defense 1991-12-08
Availability restricted
Abstract

A dielectric filled cavity structure is currently being used to estimate the dielectric constant and loss factor over a wide range of frequencies of a dielectric material which fills the cavity structure [Saed, 1987]. A full field analysis is used to compute the effective complex permittivity of the sample material based on reflection coefficient measurements of the cavity structure and associated geometrical dimensions. The method has previously been used successfully to determine the dielectric constant of materials, but limitations in the Inethod have created difficulties in accurate determination of the dielectric loss factor. The effective loss in this method yields an estimate of the total cavity loss, including both the dielectric loss and that of the cavity conductor walls.

In this dissertation a perturbation approach is used to separate the conductor loss from the total loss. The loss-free full-field analysis is used to determine the electric current at the conductor boundaries. This current is used to evaluate the perturbed power dissipated in the cavity walls based on known conductor properties. By subtracting the loss due to the conductor walls from the total loss measured in the structure, the dielectric loss and the resultant dielectric loss factor may be estimated.

Measurements are presented for sample dielectric materials. The dielectric loss tangents computed by this new technique improve the unperturbed estimates in the microwave frequency range.

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