A linear perturbation model with physical optics approximation to recover inhomogeneous surface impedance
Résumé
Inverse electromagnetic scattering problems related to objects having inhomogeneous isotropic impedance boundaries are addressed by considering small impedance variations between a measured object and a reference one. For many non-destructive electromagnetic testing, the structure geometries are known and only coated materials properties variations from reference numerical model are of interest. Consequently, the scattered field and equivalent surface current of the reference object can be precisely evaluated. We use the Chu-Stratton integral equation to express the differences of scattered far field between the measured and reference configurations in terms of surface current variation. Physical Optics approximation is used to derive a model of these surface current variations and we keep the first order term to solve a linear inverse problem. Consequently, the surface impedance can be reconstructed by a minimum norm solution in the least squares sense. Some promising numerical results on spherical geometries are presented with fixed incidence and frequency, in bistatic configuration. © Institution of Engineering and Technology.All Rights Reserved.