Extension of the Scalar Kirchhoff Approximation for Calculating the Coherent Scattering from Multi-Layers with Random Rough Interfaces

This paper deals with the electromagnetic wave scattering from multi-layered media, containing random rough interfaces. It presents an extension of a basic asymptotic model called the Kirchhoff-tangent plane approximation (KA) to multi-layers. In order to be able to derive a simple expression of the scattered intensity, further approximations must be made. Here, we focus on calculating only the coherent contribution to the total scattered intensity and apply the socalled scalar Kirchhoff approximation that makes it possible to simplify the mathematical expressions. Last, the random rough interfaces are assumed to be uncorrelated, so that a fully analytical expression of the (coherent) scattered intensity is obtained. Previous work validated this approach; this paper focuses on analysing the hypothesis of taking only one reflection inside each layer into account.