Analysis of electromagnetic scattering from planar coated flat strip and infinite strip grating

Different integral equations, based upon surface/surface and combined volume-surface formulations, are developed. For the homogeneous material coating case both surface/surface and combined volume/surface formulations are used, while for the inhomogeneous material coating case, only the combined volume/surface formulation is utilized. The electric field integral equation (EFIE), magnetic field integral equation and combined field integral equation (CFIE) are developed for the surface/surface formulation and the CFIE is developed for the combined volume/surface formulation. Both periodic and nonperiodic structures are treated in the same manner using the sampling theorem. Utilizing the respective boundary conditions, operator equations containing the equivalent currents are developed. According to the periodicity of the structure, these operator equations are formulated in the spectral domain using the Fourier transforms of the integro-differential operators. The generalized biconjugate gradient-fast Fourier transform (BiCG-FFT) method with subdomain pulse and triangle basis functions is applied to solve the operator equations numerically.<>