Frequency-selective reflection and transmission by a periodic dielectric layer
The feasibility of using a periodic dielectric layer, composed of alternating bars having dielectric constants epsilon sub 1 and epsilon sub 2, as a frequency selective subreflector in order to permit feed separation in large aperture reflecting antenna systems was examined. For oblique incidence, it is found that total transmission and total reflection can be obtained at different frequencies for proper choices of epsilon sub 1, epsilon sub 2, and the geometric parameters. The frequencies of total reflection and transmission can be estimated from wave phenomena occurring in a layer of uniform dielectric constant equal to the average value for the periodic layers. About some of the frequencies of total transmission, the bandwidth for 90 percent transmission is found to be 40 percent. However, the bandwidth for 90 percent reflection is always found to be much narrower; the greatest value found being 2.5 percent.