Phase shifts in transmission line models of thin periodic metal grids

This paper describes simple formulas for the phase shifts associated with reflection and transmission of electromagnetic waves by a thin periodic metal grid on a plane boundary between two lossless dielectrics, for the case where the wavelengths on both sides of the boundary are greater than the grid period. The phase shifts are expressed in terms of the zero-order intensity reflectance and transmittance of the grid and are correct even when the grid has loss. They correspond exactly to the phase shifts that can be calculated using the well-known equivalent-circuit models for thin metallic grids but are applicable for any thin nondiffracting layer on a dielectric boundary, for normal incidence.