A comparison of scattering model results for two-dimensional randomly rough surfaces

Bistatic radar cross sections are calculated using two modern scattering models: the small slope approximation (both first- and second-order), and the phase perturbation technique. The problem is limited to scalar-wave scattering from two-dimensional, randomly rough Dirichlet surfaces with a Gaussian roughness spectrum. Numerical results for the cross sections are compared to those found using the classical Kirchhoff, or physical optics, approximation and perturbation theory. Over a wide range of scattering angles, the new results agree well with the classical results when the latter are considered to be accurate. A comparison between the new results shows that the phase perturbation method gives better results in the backscattering region for correlation lengths greater than approximately one wavelength, while both the first- and second-order small slope approximations yield greater accuracy in the forward scattering direction at low grazing angles