TE11 Reflection of Open-Ended Circular Waveguides Application to Nondestructive Measurement of Materials

The measurement of dielectric properties of a material based on the reflection of an open-ended waveguide is a simple and nondestructive technique, which does not require to extract any sample of the material to be measured. It is therefore of interest in biomedical applications, and also in the study of the moisture content of materials. The material one wishes to measure is placed on a metallic flange which terminates the open-ended waveguide, directing the radiation within the material. The theoretical study of the problem is based upon the determination of the radiated magnetic field near the aperture, determined in terms of the transverse electric field in the plane of the aperture. An integral relationship can be elaborated, linking the relative permittivity of the material to the reflection coefficient of the propagation mode in the circular waveguide. The same technique can be used to determine the fields radiated by a diathermy applicator.