The Prediction Of Electromagnetic Environment Around Radio And Television Towers

With the development of electronic and communication technology as well as people’s pursuit of material and spiritual in our life, the space we are living is filled with more and more electromagnetic waves. Although electromagnetic waves are beneficial to our daily communication and transmission, but they may have adverse effects on human health and the electrical appliances’normal use. As the most common and concentrated source of contamination, radio and television transmission towers not only have the problem of great emission power and multi-antenna on one tower, but also near the residential areas, therefore, in the field of electromagnetic radiation, it has become the focus of attention in recent years. According to the standard of China’s industry, a new radio and television tower must be passed the assessment of electromagnetic environmental pollution before relocation or construction. So it is important to do research on the prediction of radio and television transmission towers’electromagnetic radiation.In our country, radio and television towers’electromagnetic environment prediction are always based on the HJ/T10.2-1996radiation environmental protection management guide-electromagnetic radiation monitoring instruments and methods, it has great inadequacies. Due to the long wavelength, the near-field of medium wave can be very large, if we use the method which is given in standard to calculate the field strength of near-field at this moment, large deviation will be caused, and the prediction will be useless. In regard to FM and TV broadcast, the method given in standard will be used in the condition of a flat and open environment, but the FM and television transmission towers are surrounded by growing local residents, the distance between the launch of tower and residents may be only100meters, in this case, if we continue ignore the buildings around radio and television towers, the prediction of electromagnetic radiation will have a large deviation.In this paper, firstly, we calculate the range of near-field, transition-field and far-field; moreover, the simplified formula is given in each field. A new method is proposed to calculate the field strength of near-field and transition-field, with the comparison of the existing two calculation methods and measurement data, the advantages and disadvantages of this method is given. Secondly, researches on the antennas of FM and TV transmission towers have been done, the commonly used antennas’field strength calculation methods are given. Again, three-dimensional ray tracing search method and commonly used calculation is introduced. The field strength’s calculation of reflection and diffraction is also given. Finally, based on the VS2010platform, combing with Matlab2012a and OSG,the radio and television transmission towers’electromagnetic radiation prediction system is developed using C++program language. In the prediction system, you can build three-dimensional scene, calculate propagation path and field strength. At last, through the calculation result and measurement data, the calculation error is given.