Based on the combined tangential formulation of surface integral equation,a fast algorithm is presented for calculating electromagnetic scattering from electrically large 3Dhomogeneous objects.In the algorithm,the lower triangular approximate Schur preconditioner is combined with the multilevel fast multipole algorithm(MLFMA).The coefficient matrix of the near-field coupling element is selected to set up the approximate matrix.For large problems,the incomplete LU factorization with dual threshold(ILUT) has better performance than sparse approximate inverse(SAI)of accelerating the convergence of the generalized minimal residual method(GMRES)iteration.Numerical experiments validate the efficiency and robustness of the presented fast algorithm for homogeneous dielectric objects.
