Computation of the RCS of complex bodies modeled using NURBS surfaces

The paper presents the RANURS code (radar cross section-NURBS surfaces) for the analysis of the monostatic radar cross section (RCS) of electrically large complex targets. The geometric representation of the targets is given in terms of parametric surfaces, which allow an excellent fit between the model and the real surface. The parametric surfaces used are NURBS (non-uniform rational B-spline) surfaces. This technique of modeling is used in many industries to represent complex bodies. Most of the CAGD (computer aided geometric design) tools use the NURBS format for modeling, because it can represent complicated objects using limited information. Therefore, an important feature of the code is its compatibility with most of the available CAGD codes, in order to ensure that the entire design process, involving different engineering aspects (structural, mechanical, aerodynamical, electrical, etc.) can be developed with compatible models. The scattered fields are calculated by using the physical optics and the equivalent currents methods (PO+ECM). The following contributions to the RCS are taken into account: reflected field, diffracted field, double-reflected field, and diffracted-reflected field. In addition, a method for determining the hidden parts of the targets is used. The PO+ECM approach is directly applied on the parametric surfaces, and the final expressions of the fields are given as functions of the coefficients of the numerical description of the NURBS patches.