The Measurement of Low Frequency Magnetic Field of Two Kinds of GSM900 Mobile Phone

The use ofmobile communication systems has dramatically increased over the past decade. Although many studies have been performed to determine the effect of radio frequency (RF) but less attention has been paid to the possible biological impact of exposure to extremely low frequency (ELF) components. The objective of this study is two folds. One is to design the equipments needed for the measurement of the ELF fields of two types of GSM900 mobile phone. Secondly، use a protocol suitable for an accurate assessment of the ELF fields. First a home-made search coil was provided and calibrated precisely under several experiments. Using Fast Fourier Transform، the power spectrum density of the induced voltage in the search coil was analyzed and the amplitudes of 217 Hz and its harmonics were extracted and then the distribution of magnetic field in the back side of mobile phones was determined. The values of B-field on the back side of the two kinds of GSM mobile phone were different. They were between 50 to 160 mT in Nokia 3310 and 14 to 30 mT in Nokia 8310. Considering the difference between the amplitudes of frequency components at 217 Hz and its harmonics in the two kinds of mobile phone، a range of magnetic flux density at different times in a five day period was measured. Discussion and These findings emphasize the need for considering the distribution of low frequency magnetic field from mobile phone when biological effects of magnetic fields are studied. To determine the intensity windowing effect، one must consider the physical characteristics of the fundamental frequency component wave (217 Hz) and its harmonics produced by the mobile phone similar to the one generated under a real situation