|Thesis abstract: |
My PhD research work is focused on characterization of dielectric materials for microwave and terahertz imaging systems. Novel source antenna designs are proposed and a couple of time domain data inversion techniques are implemented in order to study dielectric material characterization of solid objects. Initially, stacked patch microstrip and custom shaped horn antennas are designed to improve the antenna bandwidth and spot focusing characteristics at microwave and terahertz frequencies. A waveguide-horn-waveguide structure scheme is used to model a horn antenna in order to avoid lens correction at horn apertures, which is usually needed to enhance the spot focusing. The presented horn antennas are designed and simulated with an accurate proprietary Body-of-Revolution Finite-Element code. Interaction of electromagnetic waves with materials is studied, where the variation in magnitude and phase of the transmitted and reflected wave has been observed with and without presence of dielectric material for calibration purpose. Different data inversion techniques are developed and tested e.g, Fourier inversion and Bayesian inversion. Time and computation efficiency of the post processing techniques has also been enhanced significantly, by using proprietary code in MATLAB. The analysis and estimation of dielectric properties is mostly based on measured data and simulated results obtained using commercial software (Ansys HFSS and CAD FEKO) for the purpose of comparison.