Upgrading the hybrid finite element-boundary integral method using multilayer periodic Green´s functions

The key contribution of this paper is the enhancement of the finite element (FE)-boundary integral (BI) method to incorporate multilayer periodic Green´s functions to handle very thin substrates and superstrates in combination with arbitrary inhomogeneous radiation and scattering elements. The resulting formulation is particularly attractive for high frequency analysis of multilayer periodic structures which may be printed on physically thin but electrically thick substrates. We first present the FE-BI formulation for incorporating multilayer Green´s functions. That is followed by a discussion of the multilayer Green´s functions within a fast spectral domain algorithm implementation for carrying out matrix-vector multiplication. Results are presented for validation, including comparison with measured data for an infrared FSS on a 670 μm thick substrate.