Irradiation of a Six-Layered Spherical Model of Human Head in the Near Field of a Half-Wave Dipole Antenna

The interaction between a six-layered lossy spherical human head model and a half-wave dipole antenna is analyzed in this paper. The proposed method is based on deriving a simple form of Green´s function for multilayer lossy sphere. To derive the Green´s function of the six-layered sphere, first the Sommerfeld integral is used to expand the field of a simple electric dipole as a sum of an infinite number of the TE and TM plane waves. The response of the six-layered sphere is then calculated for each external plane wave. Finally, the total field is obtained as an integral of the responses to each plane wave. The method of auxiliary sources is then applied to model the half-wave dipole antenna as a set of unknown auxiliary current sources along the axis of the dipole antenna. By imposing boundary conditions on the surface of the antenna, the unknown coefficients can be calculated and, therefore, the electric field at any point can be obtained. In the numerical results, the important design parameters such as antenna radiation patterns, gain, and specific absorption rate are calculated at 900 and 1900 MHz. The validity of the introduced method is investigated using the full-wave electromagnetic-simulation software.