A Geometrical Optics Model of Three Dimensional Scattering From a Rough Surface Over a Planar Surface

An analytical method is described for predicting the bistatic normalized radar cross section of a rough homogeneous layer made up of a rough surface over a flat surface. The model is based on iteration of the Kirchhoff approximation to calculate the fields scattered by the rough layer, and is reduced to the high-frequency limit in order to obtain numerical results rapidly. The shadowing effect, significant for larger incidence or scattering angles, is taken into account through the use of shadowing functions. The model is applicable for moderate to large upper surface roughnesses having small to moderate slopes, and for both lossless and lossy inner media. It was validated for a two-dimensional problem (with 1D surfaces) in a preceding contribution. Here, the extension of the model to 2D surfaces is developed, and results are presented to validate the asymptotic model by comparison with a numerical reference method.