Fractional-Calculus-Based FDTD Algorithm for Ultrawideband Electromagnetic Characterization of Arbitrary Dispersive Dielectric Materials

A novel finite-difference time-domain algorithm for modeling ultrawideband electromagnetic pulse propagation in arbitrary multirelaxed dispersive media is presented. The proposed scheme is based on a general, yet computationally efficient, series representation of the fractional derivative operators associated with the permittivity functions describing the frequency dispersion properties of a given dielectric material. Dedicated uniaxial perfectly matched layer boundary conditions are derived and implemented in combination with the basic time-marching scheme. Moreover, a total field/scattered field formulation is adopted in order to analyze the material response under plane-wave excitation. Compared with alternative numerical methodologies available in the scientific literature, the proposed technique features a significantly enhanced accuracy in the solution of complex electromagnetic propagation problems involving higher order dispersive dielectrics, such as the ones typically encountered in geoscience and bioengineering applications.