Abstract
Near-field microwave imaging of dielectric composite structures, using open-ended rectangular waveguides, has shown to be a promising and powerful nondestructive testing (NDT) tool for the evaluation of these structures. Experimentally obtained raw images provide a great deal of detailed information about the properties of a specimen. To better interpret the information contained in such images it is important to develop theoretical models that explain the behavior of microwave energy inside a specimen under inspection. This will aid in the development of a methodology to obtain information about the shape and dimensions of a defect or inclusion from such image. In chapter 2 a theoretical study is conducted to expand on and demonstrate the ability of utilizing an open-ended rectangular waveguide probe to monitor the existence and to determine the position of a disbond in a layered composite structure. In chapter 3, near-field microwave imaging of dielectric composite structures using open-ended rectangular waveguides is studied experimentally. Experimental setups are presented and their operations are discussed. A near-field microwave image is the result of several factors such as the probe type (for example a rectangular waveguide, a circular waveguide, a coaxial line, etc.), field properties (i.e. main lobe, sidelobes, and half-power beamwidth, etc.), geometrical and physical properties of both the defect and the material under inspection. Chapter 4 will be devoted to study the field properties in the near-field region of an open-ended rectangular waveguide and its interaction with a dielectric material. This study will include investigating the influences of frequency and dielectric properties on the radiation pattern. In chapter 5 a study of the mechanism by which the fields interact with an inclusion will be presented. An effective dielectric constant formula will be used to model the reflection properties of dielectric structures.