A Frequency-Domain Near-Field-to-Far-Field Transform for Planar Layered Media

We report a frequency-domain near-field-to-far-field transform (NFFFT) for the numerical modeling of radiation and scattering in planar multilayered spaces. Although the results are equivalent to those of Demarest (1996), the formulation is more compact, more stable, and applicable to observation angles in the lower half space. Furthermore, the results are presented in a vector-potential formalism that is more easily adaptable to existing free-space implementations. The NFFFT algorithm can be used in any differential-equation-based finite numerical method, including but not limited to the finite-difference time-domain (FDTD) method and the finite-element method (FEM).