Analysis of the iterative Kirchhoff approximation for rough surface scattering

The iterative Kirchhoff approximation has been numerically applied to one-dimensionally rough, perfectly conducting statistical surfaces, and the backscattering predicted from the first and second iterations compared with the "exact" scattering found from the moment method. The VV second-iteration scattering proves accurate at all incidence angles with slightly rough surfaces and up to 85/spl deg/ with large-scale rough surfaces. At HH the second-iteration scattering loses accuracy at 75/spl deg/ with small scale rough surfaces and 50/spl deg/ with large-scale roughness. Scattering models based on the second-iteration IKA actually give better results at HH than would be suggested by the numerical evaluation of the IKA. The numerical results show that these models can be accurately applied to surfaces that include moderate large-scale roughness without first separating the roughness spectrum into large- and small-scale components.