Near-Field Shielding Effectiveness of 1-D Periodic Planar Screens With 2-D Near-Field Sources

The near-field shielding effectiveness (SE) of composite screens characterized by spatial periodicity along one dimension is investigated in the presence of an electric line source placed near the screen through the method of moments in the spatial domain. In particular, the array scanning method is implemented, which allows for reducing the problem of an aperiodic source in a periodic environment to that of a phased array of sources in the same periodic environment. This way, the conventional Floquet theory can efficiently be applied and the computational domain is restricted to the unit cell of the periodic structure. The metal-strip grating, the wire grid, and the wire-medium screen supported by a dielectric board are studied as examples of 1-D periodic screens, and the relevant near-field SE is studied as a function of different geometric and physical parameters. Comparisons with results obtained through classical homogeneous models are provided that show the limits of the homogenization techniques in finite-source problems. Finally, differences in SE values for such periodic structures are discussed when considering finite-source or plane-wave excitations.