FDTD, multiple‐region/FDTD, ray‐tracing/FDTD: a comparison on their applicability for human exposure evaluation

In this paper, the finite‐difference time‐domain (FDTD), multiple‐region/FDTD (MR/FDTD) and ray‐tracing/FDTD (RT/FDTD) techniques have been compared with reference to the study of the field scattered by and induced inside an exposed target. The three techniques have been validated on a free‐space radiation problem through a comparison with the MoM solution. Compression techniques have been implemented to obtain a reduction of the computational costs associated with MR/FDTD, performing an accurate evaluation of the associated errors. The applicability and accuracy of the three techniques have then been tested studying the exposure of a sphere to a half‐wavelength dipole. The obtained results have shown that the best computational performances are achieved employing RT/FDTD. However, this technique gives accurate results only in the radiative far‐field of the antenna. MR/FDTD, instead, gives accurate predictions of field distributions for a wide range of distances between the scatterer and the antenna and, thanks to the introduction of compression techniques, requires acceptable computational costs. Pure FDTD, finally, is the most suitable technique, among the three considered, when the scatterer is close to the antenna but its computational costs become prohibitive for large‐scale problems.