Numerical Dosimetry of Electromagnetic Pulse Exposures Using FDTD Method

A novel frequency-dependent finite-difference time-domain (FDTD) method, previously proposed by the author, is applied to numerical dosimetry of exposures by an electromagnetic (EM) pulse incident to biological bodies, which are characterized by four Cole-Cole relaxation terms. The proposed method applies the fast inverse Laplace transform to determine the time-domain impulse responses of the complex permittivity function and utilizes Prony's method to determine the infinite impulse response representation in the
z
-domain. The FDTD formulation for the update of the electric field is then directly derived by using the
z
-transformation. The validity of the method is demonstrated by the 3-D analyses of a homogeneous dielectric sphere and a multilayer sphere illuminated by an EM pulse. It is demonstrated that the numerical results of induced electric field distributions inside the spheres are in good agreement with those derived from Mie's theory over a broad frequency range, proving the validity of the proposed method. Finally, numerical dosimetry of a heterogeneous human head excited by an EM pulse is performed and specific energy absorption due to the pulse illumination is calculated by using the proposed method.