An electrodynamics calculation is performed for an infinite waveguide antenna array in the form of open ends of waveguides, in the near zone of which a metal-dielectric structure is located. This metal-dielectric structure is located in the "Floquet channels" and is a combination of a dielectric coating over the antenna array and horns. In this case, the horns are not a continuation of the waveguides, but are located at some distance from them. The space between the waveguides and the horns is filled with a dielectric. A system of equations that allows calculating the reflection coefficients of incident waves in waveguides is obtained.

A study of the diffraction of an electromagnetic wave on a dielectric coating with a diaphragm over an infinite waveguide antenna array has been carried out. The metal diaphragm is located at some distance from the surface of the antenna array. The influence of the geometric dimensions of a metal diaphragm and its distance from the grating surface on the modulus of the reflection coefficient of the incident wave in waveguides is investigated. Dielectric coatings with different values of the dielectric constant are considered.