A Generalized Method for Synthesizing Miniaturized Element Band-Pass Frequency Selective Surfaces

摘要

Frequency selective surfaces (FSSs) have been used extensively for a variety of millimeter and microwave applications [1]-[3]. Generally, an FSS is composed of a two-dimensional (2D), planar, array of dipole or slot antennas that are printed on a dielectric substrate. Such structures act as first-order band-stop (dipole) or band-pass (slot) spatial filters. To obtain a filtering characteristic with high out-of-band rejection, FSSs with higher-order band-pass or band-stop responses are used, in a manner similar to higher-order microwave filters. Traditionally, this is achieved by stacking multiple first-order FSS panels with a spacing of a quarter wavelength apart. This, however, results. in thick and bulky structures, especially at low microwave frequencies. In addressing this problem, new techniques for designing low profile higher-order band-pass FSSs have been reported recently [4]-[5]. In [4], a second-order FSS is introduced using non-resonant sub-wavelength elements. Whereas in [5], a third-order FSS is introduced using a combination of non-resonant and resonant elements. Both techniques, however, propose extremely thin FSS structure with overall thickness of 0>03 0. An added benefit of the proposed structures is the stability of the frequency response as a function of incidence angle of the electromagnetic wave.