Modified Waveguide Flange for Evaluation of Stratified Composites


Nondestructive evaluation of stratified (layered) composite structures at microwave and millimeter-wave frequencies is of great interest in many applications where simultaneous determination of the complex dielectric properties and thicknesses of multiple layers is desired. Open-ended rectangular waveguide probes, radiating into such structures, are effective tools for this purpose. The technique utilizes a full-wave electromagnetic model that accurately models the complex reflection coefficient as a function of frequency and material properties. While the electromagnetic model assumes an infinite waveguide flange (or ground plane), the measurements are conducted using a finite-sized flange. Consequently, the results of the electromagnetic model and those from measurements may not be sufficiently alike for accurate dielectric property and thickness evaluation. This paper investigates the effect of using an open-ended waveguide with a standard finite-sized flange on the error in evaluating the complex dielectric properties of a composite structure. Additionally, we present the design of a novel flange that markedly reduces this undesired effect by producing very similar electric field properties, at the flange aperture, to those created by an infinite flange. Finally, the efficacy of the design for evaluating the dielectric properties of a layered composite structure is demonstrated as well.


Electrical and Computer Engineering

Keywords and Phrases

Materials Characterization; Microwave; Nondestructive Evaluation; Open-Ended Waveguide; Stratified Composites; Waveguide Flange; Dielectric Properties; Electric Fields; Electromagnetism; Structure (Composition); Complex Reflection Coefficient; Materials Characterization; Millimeter Wave Frequencies; Open Ended Waveguides; Simultaneous Determinations

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version


File Type





© 2014 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Jun 2014