Enhanced Integral Equation Analysis of Multilayered Periodic Structures Useful for the Design of Reflectarray Antennas

When reflectarray antennas are designed under the local periodicity assumption, the problem of the scattering of plane waves by multilayered periodic structures has to be solved many times. The Method of Moments (MoM) in the spectral domain is the numerical technique usually employed for the analysis of these multilayered structures. Unfortunately, it is not computationally efficient since it requires the determination of slowly convergent double infinite summations. In this paper the Mixed Potential Integral Equation (MPIE) formulation of the MoM in the spatial domain is invoked to transform the slowly convergent summations into singular finite double integrals that can be efficiently computed. The novel MoM approach in the spatial domain has been found to be between one and two orders of magnitude faster than the traditional spectral domain MoM both in the analysis of multilayered periodic structures, and in the design of reflectarray antennas with cell characterization based on the local periodicity assumption.