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

Abstract

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