# Averaged Coupled-Pair Functional

The penetration of microwaves in various materials gives active microwave imaging a large potential for subsurface radar, civil engineering etc. Several inverse-scattering theories have been proposed in the scientific literature. Among them, the simplest Bom-type approach, which does not take into account multiple reflections, is valid for weakly scattering objects [1-2]. To improve the quality of reconstruction, the method based on the successive application of the perturbative algorithm was developed [3]. However, the inherent approximations of this approach are not overcome in the iterative scheme. Another class of algorithms aims to obtain the spatial distribution of permittivity by using numerical solutions of exact equations [4-6]. Unfortunately, a rate of convergence of the solution to the global minimum of cost function depends on actual contrast values, measurement error etc. That is why an importance of a priori knowledge about the object imder investigation is usually emphasized. In general, existing inversion algorithms suffer from serious problems when discontinuous profiles of high contrast, which are often encountered in practical applications, are to be reconstructed. Moreover, the frequency-swept imaging methods utilize usually reflection coefficient data measured in a very broad frequency band starting from zero frequency [1-2, 4-5]. Such methods are inappropriate from an application point of view. [c.127]

Introduction to computational chemistry (2001) -- [ c.139 ]