Transmission Line Matrix Method for Microwave Investigation of Materials

A three-dimensional transmission-line matrix (TLM) model was developed to simulate microwave investigation of materials including simulation of microwave scanning. Numerical modeling was carried out for frequencies that are commonly used in microwave nondestructive testing (NDT). Structures with local discontinuities in the electric permittivity are modeled numerically. The excitation parameters used in the numerical modeling of scanning microwave microscopy were determined based on an initial frequency experimental response obtained from a plate with known permittivity. The numerical model developed in this paper is based on the symmetric condensed node (SCN). Experimental data obtained by the authors are used to validate the numerical models presented in this work. The models developed and described in this paper have proven their viability, giving accurate results when compared to analytical solutions where these solutions are available and when compared to experimental results obtained for geometries that do not allow an analytical solution.