Equivalent circuit model of cross and circular ring FSS using vector fitting

In this paper, a rational function approximation approach called vector-fitting is adopted for developing equivalent circuit model of cross and circular ring frequency selective surfaces. The simulations of microstructure are performed with CST Microwave Studio on single - substrate for different physical parameters, angle of incidences and polarizations. Then vector-fitting is used to extract rational function from simulated data which led to direct conversion to an equivalent circuit for SPICE (Simulation Program with Integrated Circuit Emphasis) simulation for both time and frequency analyses. ADS SPICE generator is used for validating the proposed circuit models by comparing the results against the EM simulation and traditional circuit models. The developed models are within 1% of average deviation against reference data.