- Abstract: In this paper, we present a study of the radiation from a line source located inside a grounded dielectric slab covered by a metal strip grating. The array scanning method was applied to enable an efficient ldquounit cellrdquo formulation. The numerical solution was obtained with the use of the spectral method of moments. Both TM and TE cases were solved. The effects of the geometrical parameters on the propagation of guided modes and their excitation are studied.