Study on an Accurate and Efficient Design Method of Resonant FSSs Based on the Macro-Model of Units in the Basic Strip-Gap FSS

An accurate and efficient design method for resonant frequency selective surfaces (FSSs) based on the macro-model of units in the basic strip-gap FSS is proposed. Several variables are introduced in the formulas to improve the accuracy of computation. Without dielectric substrate, two effective widths are introduced in the calculation of equivalent L and C due to the current inhomogeneity caused by the gap. Novel equivalent circuit (EC) formulas are proposed after full-wave simulation and parameter fitting. Furthermore, with substrate, another two variables, the effective permittivity for inductance and capacitance, are introduced with detailed calculation equations. The results obtained by simulation and EC calculation show that not only the resonance frequencies but also the frequency responses over a wide frequency band are found to be in reasonable agreement, when the wavelength of the operating frequency is smaller than the period. For verification of complex structures and actual application, two absorbers based on cross dipole and square loop FSSs, respectively, are proposed. Good agreement is gained between the measurements of a fabricated sample working from 2.03 to 9.36 GHz, and the results obtained by EC calculation and simulation. The results verify that it is feasible to use this method in the study of more complex and novel structures which are based on resonant FSSs.