Thick FSSs for large scan angle applications

Frequency selective surfaces (FSSs) have applications in radomes, dichroic plates for antenna feed systems and quasi-optical filters for spectroscopy. Most FSSs have been printed on thin substrates, and possibly cascaded for larger scan angles. There are a limited number of theoretical discussions of thick metal FSSs. The paper presents the comparison of measurements to a mode-matching finite element numerical method for the analysis of arbitrarily thick FSS. A simple thick FSS was chosen for validation. As expected, since there are no matching dielectric layers on either side of the FSS, the TE transmission response is poor for high incidence angles. Current work is focused on the design of flat and curved radomes for large scan angle applications, and THz frequency low-loss quasi-optical filters. Our analysis tool is validated and allows us to design for frequency limits, sharpness of stop or pass bands, and impedance matching at the input and output surfaces while taking fabrication tolerances into account. The shape of the aperture can be chosen to tailor the cutoff frequency. It should also be noted that the geometry in the z-direction affects the sharpness of the transmission response while dielectric layers improve the matching at different incidence angles.