Near-field microwave non-destructive testing for defect shape and material identification

We propose a near-field approach to microwave non-destructive detection and evaluation of defects, which is based on electromagnetic (EM) numerical modeling of the forward problem and on an adjoint-variable approach to the calculation of the response Jacobians of the forward model. The measured response of the structure under test is matched to that of the forward model. The inverse least square problem is solved iteratively by an optimizer. …