Design of low profile single/dual band high-order frequency selective surfaces

Frequency Selective Surfaces (FSSs) have been the subject of intensive investigation for their widespread applications ranging from microwave systems and antennas to radar and satellite communications [1]. One common feature of the traditional FSS design techniques, widely used nowadays, is that they use resonant type constituting unit cells such as a resonant dipole, slot, circular or rectangular rings, etc [2]. In such structures, the size of the resonant elements and the inter-element spacing are generally comparable to one-third to half a wavelength at the desired frequency of operation, which further leads to a large number of the constituting elements for practical applications. Recently, a new type of frequency selective surface with non-resonant miniaturized elements was presented in [3] [4]. Both the unit cell dimensions and the periodicity of this type of FSS are considerably smaller than the wavelength. In this paper, inspired by the previous literature, a new type of frequency selective surface is presented which provides an easy method for designing low-profile band-pass spatial filters with high-order filter responses. The proposed topology contains both non-resonant (capacitive patches and wire grids) and resonant structures. It is shown that depends on the resonator dimensions, the FSS can behave as single band or dual band high order filter. In what follows, the design procedure, principles of operation, and the verification results are presented and discussed.