Effect of Sample Preparation on Microwave Material Characterization by Loaded Waveguide Technique

• Published in: IEEE transactions on instrumentation and measurement Vol. 65; no. 7; pp. 1669 - 1677
• Main Authors: Foudazi, Ali, Donnell, Kristen M.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.07.2016; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Confidence intervals; Dielectric measurement; Dielectric properties; Dielectrics; Distortion; Error analysis; loaded waveguide technique; Loaded waveguides; material characterization; Mathematical analysis; measurement error; microwave nondestructive testing; Microwaves; sample preparation; Samples; Statistical analysis; Statistical methods; Transmission line measurements; Waveguides; measurement error; Dielectric properties; loaded waveguide technique; material characterization; microwave nondestructive testing; statistical analysis; sample preparation
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2016.2540840

Microwave material characterization is an important nondestructive evaluation tool, as many physical and chemical properties can be related to a material's dielectric properties. These properties can be measured using a number of methods including the loaded waveguide technique. This method requires that a sample be placed in a waveguide sample holder and subsequently utilizes measured complex reflection (S 11 ) and transmission (S 21 ) properties to calculate the sample's dielectric properties. As such, it is important that the sample be prepared carefully, as the dielectric property calculation assumes a perfect (ideal) sample geometry. However, in practice, samples are oftentimes prepared by hand, resulting in a distorted sample geometry. This paper presents a simulation and measurement study on a number of potential sample preparation errors and the effect of these errors on calculated dielectric properties. Finally, a statistical analysis (including mean, standard deviation, coefficient of variation, and confidence interval) was applied to provide a method by which calculated dielectric properties (even when imperfect samples are used) can be checked to ensure that proper accuracy of the results has been achieved.