Comparison between different types of green's function factorization for the BMIA/AIM method

Three different formulations that allow to extend the BMIA/AIM method to the analysis of large dielectric stratified structures are introduced. These techniques lead to an approximate form of the multilayer Green's function, valid in the region where the thickness of the substrate can be considered small compared to its transverse dimension. This approximate form results as the product of three terms: two dependent by the source and observation longitudinal position, the other by its transverse distance. The first technique makes use of a suitable description of the Green's function in terms of discrete complex images. The remaining ones deal with the evaluation of the Green's function along the steepest descent path integration and a least-squares interpolation formulation, respectively.