Review of some inverse methods in electromagnetics

In this paper we present a brief review of some methods for solving the inverse problem in electromagnetics, methods that are useful for the problem of profile inversion of a layered medium whose complex refractive index varies as a function of depth or the radial distance. The scope of the paper is limited to a discussion of rigorous techniques only, and the numerical schemes based on the parameter estimation algorithms, or approximate methods, e.g., migration techniques and the ray methods, are not included.