Fast inhomogeneous plane wave algorithm for scattering from objects above the multilayered medium

The previously developed fast inhomogeneous plane wave algorithm is adapted to the analysis of the scattering from the objects above the multilayered medium. Based on the similarity of the inhomogeneous plane wave expansion o f the Green's function encountered in the layered medium study to its free space counterpart, the proper steepest descent path can be defined. By usin g the interpolation and extrapolation techniques, the translation matrix is diagonalized, The contributions of the pole and branch point, resulting fr om the deformation of the integration path, can be handled easily. Comparin g with the previously developed methods in this area, this algorithm is sim pler, more efficient, and more general. The multilevel fast inhomogeneous p lane wave algorithm has been implemented and the numerical results show tha t O(N log N) computational complexity of the algorithm is achieved. The alg orithm is validated by comparing the results from a conventional method of moments program.