Fast far field approximation for calculating the RCS of large objects

Provides an RCS estimation technique called the fast far field approximation (FAFFA). The idea of the method is to compute the interactions between elements using different methods depending on the electrical distance between the elements. When the distance is small, the exact interaction is calculated; When the distance is large, the far field approximation is used. The field interactions are calculated iteratively using the conjugate gradient (CG) method. The iteration process takes into account the higher order terms in GO, PO or PTD approximations. The algorithm has a computational complexity of O(N/sup 1.33/) and memory requirement of O(N) for N unknown problems. The authors first present the formulation using a two dimensional electrical field integral equation (EFIE) for the TM wave incident case. Then they give numerical simulations for both two dimensional and three dimensional targets.