A technique for the analysis of the scattering from gently undulated finite surfaces

One of the frequently encountered problems in radar applications is that of determining the radar cross section (RCS) of objects with finite size and whose surfaces are not really flat. The method of moments (MoM)-based calculations are widely used, but if the surface to be analyzed becomes large in size, the CPU memory and runtimes increase dramatically. We introduce a novel approach to calculate the induced current density on gently undulated finite surfaces. This approach is based on the plane wave spectral (PWS) decomposition and on the small perturbation (SP) theory. First, we replace the original finite surface by an infinite one, but illuminated by a windowed excitation field; then, for each plane wave spectral component we calculate the induced current density via the SP theory. Finally, we sum these current densities with the appropriate phase shift and weight, to get the total induced current. Once the total induced current is known, other related parameters, as for instance the RCS, can be easily calculated.