Microwave imaging by mixed-order discontinuous Galerkin contrast source inversion

Recent developments in microwave imaging algorithms have led to contrast source inversion algorithms based on finite-element method forward solvers. The resulting algorithms are flexible in their ability to support a variety of microwave imaging environments, including metallic boundaries of practically arbitrary shape. One limitation of low-order finite-element based imaging algorithms is that, unless an explicit dual mesh scheme is imposed, the discretization of the contrast and contrast sources is implied by the mesh that describes the underlying field discretization. High-order expansions for the fields, contrasts and contrast sources overcoming this deficiency. In this work we present a high-order contrast source inversion method for dielectric targets that supports distinct expansion orders for the fields, contrasts and contrast sources. High-order expansions for the contrasts essentially decouples the image reconstruction from the underlying mesh discretization. The field solver is based on a high-order frequency-domain discontinuous Galerkin formulation of Maxwell´s curl equations. Results presented for both numerical and experimentally collected transverse magnetic data-sets illustrate the potential of the proposed method.