The application of open-ended coaxial sensors for dielectric measurement of finite thickness composite sheets is studied. Expressions for calculation of the complex aperture admittance for two geometries are presented. These expressions are used to calculate the dielectric constant of infinite half-space as well as finite thickness slabs. A more efficient method of such calculations, using a personal computer, for low to medium loss dielectrics is demonstrated. The question of when a dielectric layer may be considered as infinitely thick is also addressed, and examples are presented. A different calibration technique (compared to the conventional ones) is described and successfully implemented. This calibration technique utilizes a dielectric sheet with known dielectric properties and thickness. Measurements for different airgaps between the open-ended coaxial line and the dielectric sheet are used to perform and enhance the calibration. The results of this calibration technique and several subsequent measurements are presented and discussed.


Electrical and Computer Engineering

Keywords and Phrases

Airgaps; Calibration; Calibration Technique; Complex Aperture Admittance; Dielectric Constant; Dielectric Measurement; Dielectric Properties; Finite Thickness Composite Sheets; Infinite Half-Space; Nondestructive Testing; Open-Ended Coaxial Line; Open-Ended Coaxial Sensors; Composite Testing and Evaluation; Electromagnetic Formulation-Probe Development And Antennas; Material Characterization

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 1995 Institute of Electrical and Electronics Engineers (IEEE), All rights reserved.

Publication Date

01 Dec 1995