Reconstruction of dielectric and velocity profiles in pipelines through an electromagnetic inverse scattering technique

An electromagnetic method is proposed for the retrieval of dielectric parameters and velocity profiles inside pipelines. It is based on the solution of an inverse scattering problem for cylindrical configurations. An axially moving multilayer elliptic cylinder is assumed. Relativistic velocities can be considered, too. The measurement of the field vectors is assumed to be performed around the cylinder in a given observation domain. The related inverse problem is formulated through series expansions in the spatial domain in which the dielectric properties and velocities of the various layers are the problem unknowns. The resulting equations are discretized and the obtained ill-posed algebraic system is recast as an optimization problem and solved by using the Artificial Bee Colony method, which is a stochastic optimization method. The paper includes an outline of the direct scattering formulation for the multilayer elliptic cylinder and a detailed description of the considered inverse problem. Several numerical results are reported in order to preliminary assess the capabilities and limitations of the proposed approach.