Estimating the error of the FDTD method for complex inhomogeneous models

The finite difference time domain (FDTD) technique is routinely used to calculate the distribution of electromagnetic fields in complex geometries, e.g., a cellular phone held next to a human head. Two possible sources of error in this method are: a) the modeling error from discretizing complex inhomogeneous objects (head, phone, etc.) on a uniform grid, and b) the numerical error associated with the finite difference scheme. Typically, error estimates are not provided with such FDTD calculations since the conventional method of using the finer mesh to compute these requires too much computer memory. In this paper we propose a method of estimating the total error in using the FDTD technique for very complex inhomogeneous media, like realistic head models, which does not require mesh refinement.