The Study Of Mobilephone Signal Blocker's Electromagnetic Field And The Development Of Evaluation System

In recent years, the mobile phone signal blockers are extensively used, although the using of these equipments in particular places in order to restrict cell phone has come true, but the high frequency electromagnetic wave transmitted by them may cause damage to human body and meanwhile bring serious interference to mobile communication systems.Since 2007, Henan province carried out a provision of using mobile phone signal blockers in all college entrance examination rooms. This provision caused many parents'strong disagreement and caused many arguments in society. Although by using mobile phone signal blockers in examination rooms can effectively eliminate examinee to cheat by using wireless communication tools, and maintain the order of an exam, but the electromagnetic radiation of these devices may cause potential damage to the examinee's health, and may influence the examinee bring their ability into play. In addition, "innocent" cell phone users'signals are shielded usually can be seen in reports from time to time.In order to regulate the use of mobile phone signal blockers, it is necessary to have a quantitative research of the safe distance between blocker and human body and have a quantitative research of the device's effective shielding range and the influence to mobile communication systems.Firstly, this paper introduces the working principle of the mobile phone signal blocker, and the possible damage to human body of the high frequency electromagnetic. Aimed at the worries of the examinee's parents, I established a electromagnetic model of classroom based on the classroom of Zhengzhou university south campus's teaching building, and established a electromagnetic model of mobile phone signal blocker based on the BNT-Ⅰtype of mobile phone signal blocker which is a production of Tianjin Bonot Corporation. Then I used XFDTD simulation software to compile a calculation simulation procedure based on FDTD algorithm, calculated the electric field intensity distribution in the classroom when using the mobile phone signal blocker, record the data of the examinee seat height 1.3 meters. According to the National Electromagnetic Radiation Protection Regulations (GB8702-88) and the Radiation Protection Management Guidelines-Environmental Impact Assessment of Electromagnetic Radiation and standards (HJ/T10.3-1996), I carried out a quantitative analysis of the mobile phone signal blocker's electromagnetic radiation, and gave out the minimum distance between the mobile phone signal blocker and human body. This research can make the examinee not to cheat in the examination and at the same time ensure the electromagnetic radiation under the national standards prescribed limits when using mobile phone signal blockers. In order to verify the correctness of the simulation program, I did a practical measurement of the mobile phone signal blocker's field distribution in the classroom, then I compared calculated results with measured result, the measured results verify the correctness of the model calculation program. This paper also optimized the model program, which guarantees the accuracy and. meanwhile consume the computer memory as little as possible.Secondly, this paper introduces the propagation losses during the signal transmission, and then gives the study of mobile phone signal blockers according to the relevant standards of the communications industry and radio wave propagation models. At last, I gave out this mobile phone signal blocker's effective shielding range and the influence to mobile communication systems.Finally, I used Visual basic 6.0 to produce a system interface, and design the mobile phone signal blocker electromagnetic radiation effect evaluation system. This system was designed according to the practical needs for the man-machine interface. It can let users call XFDTD software to establish the models of classroom and to calculate them. It also can deal with the calculated results, and finally show out the electric field intensity distribution in the classroom when the position of mobile phone signal blocker was fixed. So that people can clear understanding the electromagnetic radiate influence of the mobile phone signal blockers. This system is also available user to input the radiated power of mobile phone signal blockers, the placed height of cell phones, and the height of mobile communication stations, etc. The system can calculate the mobile phone signal blocker's effective shielding range and the influence to mobile communication systems. This system is used to regulate mobile phone signal blockers and it has certain directive significance.