Microwave nondestructive testing and evaluation of electrical properties of lossy materials

The measurements of reflection and transmission complex scattering (S-) parameters are generally utilized for characterization of electrical properties of materials at microwave frequencies. There are three disadvantages of these measurements: (a) ambiguities in phase; (b) errors caused by shifts in calibration planes; and (c) phase uncertainty of reflection scattering parameters of low--loss materials. The connection between the characterization of electrical properties of materials and the application of these measurements in industrial-based applications is simply lacking. The first part of this dissertation focuses on two new measurement methods to fill this gap by eliminating the aforementioned disadvantages.;In the literature, microwave nonresonant transmission/reflection methods for materials electrical characterization eliminate either the dependency of calibration-plane on measurements or the dependency on thickness in the measurements. A recently proposed method to simultaneously eliminate these dependencies is inadequate for both complex permittivity and complex permeability measurements. In the second part of this dissertation, we propose a unique technique for calibration-plane invariant and thickness-independent complex permittivity and complex permeability determination of granular and/or liquid materials.;Cement-based materials (cement paste, mortar, concrete, etc.) are the most widely used construction materials in the world. Knowledge of mechanical, mixture proportion, chemical properties as well as electrical properties of such materials is important for evaluation of their quality and integrity. The methods commonly used in civil engineering for characterizing their mechanical properties are generally destructive. The third part of this dissertation presents microwave nondestructive reflection and transmission properties of young mortar specimens with different w/c ratios over their early curing periods and hardened mortar and concrete specimens with different w/c ratios over their late curing periods.;A direct application of available microwave methods in the literature to industrial-based applications may not be appropriate since these methods generally necessitate expensive instruments. Therefore, there is a need for a simple and relatively inexpensive microwave sensor for electrical characterization of materials in industrial-based applications. In the final part of the dissertation, we propose a microcontroller-based microwave free-space sensor for measurements of electrical properties of lossy materials.