Homogenization of composite consisting from dielectric slab and wire grid assuming negative and non-negative permittivity, a comparison

In this paper, homogenized model for composite consisting from a dielectric slab and printed wiregrid is derived by use of a global optimization technique. Due to the presence of wiregrid, the effective permittivity is negative at low frequencies similarly to wire medias. In our approach, the derivation of the homogenized model assumes that both the TE and TM polarized transmission coefficients for 0 to 60 degree range of angles of incidences are considered during optimization. As a result the equivalent model of the composite structure predicts accurately transmission through the composite in a complete range from 0 to 90 degrees. The homogenized model for the composite is tested in a commercial EM simulator which enables use of negative material parameters. A very good agreement between behavior of the original structure and its homogenized model within EM simulation program is observed. Except of the model assuming negative permittivity, model with a non-negative material parameters is presented and compared with the model having negative permittivity.