Calculation of Physical Optics Integrals Over NURBS Surface Using a Delaminating Quadrature Method

Physical optics (PO) is a widely used radar cross section (RCS) estimation approach for electrically large-scaled objects, and it is finally reduced to the calculation of highly oscillatory integrals. In this paper the PO integrals over non-uniform rational B-spline (NURBS) surfaces is proposed to be calculated with a delaminating quadrature method. The method has the merits of being very stable, accurate, and fast, and its computation cost does not increase with frequency. Moreover, in order to keep these good properties for PO integrals involving critical points (stationary phase point, resonant point), a scheme of integral-subdividing is proposed, and new approaches for locating the critical points are also presented. Numerical examples of flat surface, cylindrical surface, and spherical surface well show the advantages of the new method.