Date of Award

9-1-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Department of Electrical and Computer Engineering

First Advisor

Michael J. Havrilla, PhD

Abstract

As the use of anisotropic materials in electromagnetic applications continues to proliferate, it becomes increasingly important to develop non-destructive evaluation methods for those materials in their installed configuration. In many applications, these materials are permanently affixed onto conducting bodies to reduce unwanted reflections, making it impossible to collect S21 or S12 transmission measurements as used in many techniques based on the well-known Nicolson-Ross-Weir algorithm. It also makes it impractical to reorient the sample to collect orthogonal measurements aligned with the optical axes of the anisotropic material. The goal of this research is to develop a two-reflection coefficient measurement method for extracting constitutive parameters from non-destructive interrogation of a conductor backed, non-magnetic uniaxial material using a single flanged rectangular waveguide probe. First, this dissertation presents motivation and background on complex media and their characterization. Next, a scalar-potential formulation is presented to derive Green functions describing a parallel plate region containing two layers of uniaxial material. Two measurement techniques based on those Green functions are then developed and analyzed via uncertainty analysis. One technique is validated using laboratory measurements compared to those from a mature destructive technique. Next, the advantages and disadvantages of both proposed techniques are discussed as well as suggested areas of promising future research. Ultimately, this work demonstrates that nondestructive characterization of conductor-backed uniaxial materials is not only possible, but can be achieved in an efficient, practical manner with results on par with mature destructive techniques.

AFIT Designator

AFIT-ENG-DS-19-S-004

DTIC Accession Number

AD1084400

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