Influence of single and multiple-layer dielectric substrates on the band spacings available from a concentric ring frequency-selective surface

A modal analysis is presented for a frequency-selective surface, consisting of a periodic array of elements printed on a multiple-layer dielectric substrate. The effect of the substrate thickness on the plane-wave reflection/low frequency transmission-band frequency ratio of an array of concentric rings is studied experimentally and theoretically, with the particular aim of attaining ratios of the order of 2 · 3. The influence of the skin separation in a three-layer substrate is also described.