A Generalized Method for Synthesizing Low-Profile, Band-Pass Frequency Selective Surfaces With Non-Resonant Constituting Elements

We present a comprehensive synthesis procedure for designing low-profile, band-pass frequency selective surfaces composed of non-resonant constituting elements. The proposed FSSs use arrays of sub-wavelength periodic structures with non-resonant constituting unit cells with unit cell dimensions and periodicities in the range of 0.10 lambda(0) - 0.15 lambda(0), where lambda(0) is the free space wavelength. The main advantages of this type of FSS, compared to traditional ones, are that they allow for the design of low-profile and ultra-thin FSSs that can provide sharp frequency selectivity and stable frequency responses as functions of angle and polarization of incidence of the EM wave. An N-th order FSS designed using this technique typically has an electrical thickness in the order of similar to (N - 1)lambda(0)/30 which is significantly smaller than the overall thickness of a traditionally designed N-th order FSS (similar to (N - 1)lambda(0)/4). The proposed synthesis procedure is validated for two FSS prototypes having third-and fourth-order band-pass responses. Principles of operation, detailed synthesis procedure, measurement results of a fabricated prototype, and implementation guidelines for this type of FSS are presented and discussed in this paper.