Forward and Inverse Scattering Models for waveguide sensors applied to nondestructive microwave sensing applications

Abstract

This thesis deals with the nondestructive evaluation of homogeneous and non homogeneous dielectric materials at microwave frequency. The thesis presents a forward and inverse scattering modeling technique for the analysis of open ended waveguide based newlinesensor interaction with multilayer materials. The technique has been used to detect the behavioral change in the bulk properties of the material. Hence, the technique has been applied to nondestructive microwave sensing applications, which is an emerging technique for evaluating integrity of materials, components or structures or quantitatively measure certain characteristics of an object for industrial, agricultural, environmental newlineand health care applications. A quantitative mathematical model of the sensor interaction with the material under test (MUT) is the backbone of any nondestructive microwave sensing technique for complete characterization of materials and provides the newlinenecessary foundation for the system development. The developed model in this thesis, which is implemented in C++ language and made available for open source community, overcomes the limitations of singularities and tail integration issues of existing near field newlineplane wave spectrum theory based model. The model is generalized for multiple waveguide based sensors for various nondestructive microwave sensing applications, such as bone mineral density analysis and monitoring harmful contaminants in the water. The newlinedeveloped model has been tested experimentally on laboratory prepared samples and shows good agreement with the data from literature. The model also demonstrates excellent computational efficiency compared to commercially available finite element method based model. Further the model is used to develop a compact, reconfigurable and low cost system prototype using software defined radio for real time monitoring of contaminants in water. The experimental outcomes are practically identical to vector network analyzer. However, the experimental system developed is cheaper and have small...