Convergence of a Single-Frequency FDTD Solution in Numerical Dosimetry

In this paper, we propose a new approach for determining convergence in finite-difference time-domain (FDTD) method for numerical dosimetry at a single frequency. Both amplitude and phase of the FDTD calculation are simultaneously determined and traced in the time domain in order to evaluate the convergence of the solution and terminate the FDTD computation. Validity of our approach has been demonstrated via dosimetry of a homogeneous dielectric sphere in comparison with Mie's analytical results at frequencies from 100 kHz to 100 MHz. Induced SARs calculated by the proposed approach are in good agreement with Mie's results, having differences in the whole-body average SAR for less than 9%. It is also found that convergence of the FDTD solutions is related only to permittivity, conductivity, and time-step interval. Finally, the proposed approach has been applied to analysis of an inhomogeneous realistic human body of a Japanese adult exposed to an electromagnetic (EM) plane wave and to localized EM fields radiated from a wireless device at intermediate frequencies around 10 MHz.