Simulation of Radar Scattering from Rough Surfaces

摘要

The project established computer simulation as a tool for studying scatteringfrom randomly rough surfaces. The proposed methods to be investigated included the standard moment method and the integral equation method (IEM). The minimum size was investigated for the surface patch necessary to obtain the scattering cross section per unit area, which should be the same as obtained from an infinite surface patch when the method used was the standard moment method. Five points per wavelength, or per surface correlation length (whichever was the smaller), were needed and the minimum surface patch should be at least seven electric wavelengths, or surface correlation lengths (whichever was the larger). The minimum number of surface patches to be averaged to obtain a satisfactory estimate of the scattering coefficient was 25. This means that the smallest number of unknowns to be evaluated was (35 x 35) for a scaler problem and 2 times (35 x 35) for a vector problem. To determine this many unknowns for a scalar problem one needs to invert a matrix size of 35 sq by 35 sq in the moment method. In general, the size of the problem would be larger and hence the integral equation method was investigated. The IEM was a better method than the moment method in that it required much less memory. It required a much greater computational time. For this reason another method called the frequency domain method (FDM) was considered towards the end of the project. The FDM was the preferred method in two-dimensional surface scattering problems because it was more efficient in both memory and computational time. Due to time limitation, extensions of the FDM to three dimensional scattering problems are yet to be done. (jhd)