Study of the dichroic behavior of waveguides with dielectric gratings

The use of waveguides with a dielectric grating, as dichroic surfaces in the millimeter wave band was proposed by Bertoni et al. (1989) as an alternative to a periodic array of conductors used in feeders of antennas in various frequency bands, considering that in this frequency band the dielectric losses are smaller. In this paper the potential use of these periodic structures is explored, extending the considerations made by Bertoni and showing that the selective behavior is modified when the periodic layer configuration is modified by introducing dielectric slabs in its characteristic cell. The analyses also show that this behavior changes by changing the incidence angle of the plane wave that excites the structure, the height/period ratio of the periodic region and the electric characteristics of the medium that confines (loads) the periodic layer. In addition an expression is presented for an analytical estimation of how many times and the corresponding frequency values for which the fundamental mode is reflected by the structure with maximum intensity.