The two-scale model for random rough surface scattering

Wave scattering from rough surface is important in many diverse areas, including radio communications, microwave remote sensing, underwater acoustics. The recent interest in bistatic radar, or the study of radio link above the sea surface, has led to the need for information concerning bistatic reflectivity of clutter viewed by such systems, particularly for near grazing incidence. The problem of developing a model for a rough surface is very difficult since at best σ is dependent upon (at least) radar frequency, geometrical parameters, physical parameters, incident and observation angles, and polarization. Therefore, it is necessary to restrict the areas of applicability of such models. A first major new consideration in this paper is to study the domain of validity of the Kirchhoff and small-perturbation rough surface scattering models (in the bistatic case). Comparisons between the numerical calculations and the models are presented for various surface rms height and correlation length both normalized to the incident wave number (denoted by kσ and kL, respectively). These two parameters form a two-dimensional space, into which the approximate regions of validity are established. The second new major consideration is the development of the theoretical composite model describing bistatic reflectivity. One application is implemented for the ocean surface case. Numerical results for the cross sections are compared to chose found using Kirchhoff approximation (Physical Optics), small-perturbation model, and the phase perturbation technique