Microwave Imaging of Plain and Reinforced Concrete for NDT Using Backpropagation Algorithm

The focus of this paper is implementation of backpropagation algorithm as a solution for the inverse source problem for microwave imaging of plain and reinforced concrete targets for nondestructive evaluation (NDE). The data used in imaging was obtained from numerical simulation of microwave scattering by concrete targets using a finite difference-time domain (FD-TD) technique. Electromagnetic (EM) properties of concrete were obtained from previous experimental research. Simulations were performed using a Gaussian pulse wave excitation for dry concrete cylinders with and without a rebar at the center. Images reconstructed using the backpropagation algorithm showed the potential of the method for concrete NDE while drawing attention to its limitations mainly due to the linearizing assumptions in the algorithm’s formulation.