Fast far field approximation for calculating the RCS of large objects

In many high frequency scattering problems, the scatterers are large compared to wavelength. When high frequency is required, exact solution is impossible with current computer resources. In this case, approximate methods are very helpful. Another RCS estimation technique is thus presented, called the fast far field approximation. This technique computes the interactions between elements using different methods depending on the electrical distance between the elements. The field interactions are calculated iteratively using conjugate gradient method. A formulation using two dimensional electrical field integral equation for TM wave incident case is also presented. Then numerical simulations are given for both dimensional and three dimensional targets.