The Study On Electromagnetic Radiation Distribution Of The Mobile Communication Base Station In The Environment

With the production development and the social progress, the use of cell phone has spread to every corner of the world. It has made a great convenience for the people's life and production. Now more and more base stations coming into being in order to meet the needs of the signal anytime and anywhere. Meanwhile, the electromagnetic radiation also becomes a focus of attention during the construction and operation of the mobile communication base station.In order to make the public have a better understanding of the electromagnetic radiation about the base station, avoid causing unnecessary panic, it is very important to make a study of the intensity and characteristic about the base station electromagnetic radiation.This thesis was predicated on the national standard "Electromagnetic Radiation Protection" (GB8702-88) and "Guidelines for Environmental Management of Radiation-Electromagnetic Radiation of Environmental-Impact Assessment Methods And Standards"(HJ/T10.3-1996)released by National Environmental Protection Agency, took the mobile communication base stations as the object of Study, according to the prediction equations of electromagnetic radiation axial power density in "Guidelines for the Environmental Management of Radiation Monitoring Instruments And Methods of Electromagnetic Radiation" (HJ/T10.2-1996),theoretically predict the axial propagation characteristics of electromagnetic wave, the intensity of electromagnetic radiation on base station and so on, and calculate the security distance about the various mobile communication base stations.The paper selected eight hundred and sixteen base stations built in Hubei province in 2007,2008,Statistical analyzed of a large number of monitoring data. And selected a number of typical base stations, measured the electromagnetic radiation in the horizontal and vertical direction in detail.The results are as follows:1.The electromagnetic radiation intensity in the region nearby base station is: antenna front>antenna back>antenna side. The electromagnetic radiation in main lobe direction of antenna with the distance it showed a trend as first increases and then decline, there was a maximum on electromagnetic ground projection point. 2.Antenna radiation lobe in vertical direction have a certain width, the measurement results on five typical base station in vertical direction showed that for the building opposite the station, the maximum value of electromagnetic radiation appeared in the floor closed with the antenna height. It meaned the maximum value of electromagnetic radiation was in main lobe direction of antenna, deviating from the main lobe direction will lead to the strength reducing, the more obvious the greater the reduction.3.According to the national standard "Electromagnetic Radiation Protection" (GB8702-88) and "Guidelines for Environmental Management of Radiation-Electromagnetic Radiation of Environmental Impact Assessment Methods And Standards" (HJ/T10.3-1996)released by National Environmental Protection Agency, the protection distance about all-in-one and two-in-one base stations were 5m,8m and 6m, 12m.4. By comparing, there was a good agreement between the theoretical predictions and actual monitoring data besides some bias, the probably reasons may be:①the Prediction results were calculated with the nominal power but the real operation power did not reach it.②Theoretical predictions only study the electromagnetic radiation for base station antenna, not including the.other radiator in external environment, but the actual measurement of electromagnetic radiation was also include other electromagnetic waves,so measurement is bigger than expected sometimes.③Angle, erection methods and the height of the antenna all effect the monitoring results, predict results was the electromagnetic radiation in axial direction, it is the maximum value for the same distance. However, the actual measurement point position often have a certain deviation from the axial direction, result in the measurement result be smaller than the predicted value.④The diffraction, diffraction, reflection by building and air barrier or other factors all affect the actual monitoring results.5.According to the measurement of eight hundred and sixteen base stations built in Hubei province in 2007,2008,statistical analyzing of 4161 monitoring data. We can see the trend of the electromagnetic radiation declining with distance, which was consistent with theoretical prediction results.6.Actual monitoring data showed that maximum measured surrounding base station was within the 1-5m,measurement decreased with the increase of the distance,there was a greater impact within 15m, and most of the measurement results was about 0.4V/m, basically close to the background level.7.In this study, the maximum value of all measurements is 4.76V/m, it was equivalent 6.01μW/cm2 in power density. All measurement results are in line with the standard 40μW/cm2(12V/m) in "Electromagnetic Radiation Protection" (GB8702-88) and 8μW/cm2 (5.37V/m) in "Guidelines for Environmental Management of Radiation Electromagnetic Radiation of Environmental Impact Assessment Methods And Standards" (HJ/T 10.3-1996).