Radiation From Directive Antennas Close to Human Tissue

Abstract

The possibility of reducing the radiation from mobile phones into the human body by using a directive antenna is studied. The antenna analyzed is a Huygen's source, that is, a theoretical directive antenna consisting of an incremental electric dipole perpendicular to an incremental magnetic dipole. The relative power absorption is calculated for three different models of the human head. The simplest head model is a lossy dielectric half space, a somewhat less rough model is an infinitely long lossy cylinder of circular cross section and the most exact head model is a homogeneous lossy dielectric sphere. A comparison with a Hertzian dipole, i.e. an incremental electric dipole, at the same positions is done. The different head models are used in order to investigate to what extent it is possible to simplify the model of the human head while still getting useful results. The results show that the relative power absorption for the Huygen's source is substantially lower than that for a Hertzian dipole. When the antenna is placed 2 cm from a lossy dielectric homogeneous sphere of radius 10 cm, the relative absorption is 5 dB lower for the Huygen's source compared to a Hertzian dipole. It is also shown that when the antenna is placed close to the head, the results for the different head models are fairly similar, especially when the antenna is a Hertzian dipole.