A sixth-order fast algorithm for the electromagnetic scattering from large open cavities

In this paper, a sixth-order fast algorithm is presented for solving the electromagnetic scattering problem from a rectangular open cavity embedded in an infinite ground plane. Firstly, a sixth-order compact finite difference scheme is employed to discretize the scattering problem described by the Helmholtz equation with a nonlocal boundary condition. Then, exploiting the discrete Fourier transformation in the horizontal and a Gaussian elimination in the vertical direction presented by [2], the discrete system reduces to a much smaller interface system. An effective preconditioner is developed for the Krylov subspace iterative solver to solve this interface system. Numerical results show the remarkable efficiency and accuracy of the new algorithm.