Effective permittivity of mixtures: Numerical validation by the FDTD method

The present paper reports the results of an extensive numerical analysis of electromagnetic fields in random dielectric materials. The effective permi ttivity of a two-dimensional (2-D) dielectric mixture is calculated by FDTD simulations of such a sample in a TEM waveguide, Various theoretical bound s are tested in light of the numerical simulations. The results show how th e effective permittivity of a mixture with random inclusion positionings is distributed, All possible permittivity values lie between Wiener limits, a nd according to FDTD simulations the values are almost always between Hashi n-Shtrikman limits, Calculated permittivity distribution is also compared w ith theoretical mixture models. No model seems to be able to predict the si mulated behavior over the whole range of volume fraction.