Novel synthesis formulas to design square patch frequency selective surface absorber based on equivalent circuit model

摘要

A new procedure is presented to design electromagnetic absorbers based on resistive square patch frequency selective surface (FSS) over grounded dielectric. The periodicity (p) and the distance between two adjacent squares in the lattice (w) are two unknowns to be solved, given the thickness and permittivity of the substrate, surface impedance of the square patches and the desired reflectivity in some specified frequency. Equivalent circuit model and transmission line method are employed here. Previously reported analysis formulas to calculate the square patch FSS admittance are exploited and novel synthesis formulas are extracted based of them. The final synthesis equations to calculate p and w are presented in term of polynomials. Usually an absorber is supposed to have a maximum reflectivity r in a frequency band [f(1), f(2)]. The (p, w) pairs for reflectivity less than r in f(1), define an area in p-w plane. The intersection of the so-called area with the similar one defined by f(2) specifies all possible (p, w) pairs. Finally the results are tested and verified by the commercial full wave simulator Ansys-HFSS as well as some experimental design. There is a good agreement between the expected results with the full wave analysis and practical test.