Development of a Measurement System for Nondestructive Determination of Dielectric Constant and Magnetic Permeability of Materials, Using an Enhanced Microwave Chamber Disturbance Method

The microwave chamber disturbance method (CDM) is a commonly used procedure for determining the electromagnetic properties of materials in the microwave frequency range. This method is based on the change in the resonance frequency and the quality coefficient of a measurement chamber due to the penetration of the sample at the location of the maximum electric or magnetic field, depending on the nature of the parameter under study. The main limitation of the CDM is the requirement that the sample size must be small so as not to have a negligible effect on the geometry of the fields inside the chamber. In this paper, we propose an enhanced CDM for accurate measurement of dielectric constant and magnetic permeability of materials with very low error rates. The chamber consists of a rectangular waveguide with a cap that fits the location of the sample. This arrangement provides a suitable measuring device that minimizes the measuring errors, including the uncertainty in the perforated plate and use of liquid adhesive for sample-waveguide attachment. To validate the accuracy of the proposed method, the predicted values of dielectric constant and magnetic permeability of several sample materials are compared with their actual values and the error rate of this proposed method has finally reached less than 1.5%