Modeling of hand-held receiving antennas in the presence of a human head

The topic of deleterious health effects, caused by the interaction of electromagnetic waves with a biological object, has been the subject of extensive studies by a number of researchers in recent years. It has been found that there is a substantial amount of EM-coupling from the antenna to the human body, when the latter is allowed to make direct contact with the ground. Furthermore, the RF power absorbed by the human body has been found to be maximum when its height is nearly equal to the resonant length, which occurs when the frequency is on the order of 90 MHz. The objective of this paper is to carry out a study of antenna interaction with a human head for frequencies in the vicinity of 1 GHz, which corresponds to the GSM (pan-European mobile telephone system) band. No absorption peaks caused by resonance effects are expected to occur at these high frequencies. Furthermore, for radiated power levels less than 6 W, there are no indications of thermal risk when operating a hand-held portable telephone at 450 MHz and 900 MHz. None the less, modifications of other attributes of the antenna, viz., the input impedance, the radiation pattern and the gain, can be significant in the GSM band.