The Electromagnetic Environment Forecasting And Measurement Around Broadcast Television Emitting Tower

This project is about electromagnetic environment around Henan broadcast television tower. when the broadcast television coverage becomes widespread, the electromagnetic radiation is always a popular topic of the social attention. It is important to set up a precise, practical and field intensity forecasting mold of broadcast television electromagnetic radiation for the city planning, health of citizen and environment evaluation.Firstly, this project discussed the principles of the common broadcast television antennas such as batwing antenna, dipole antenna and loop antenna, as well as the analysis and calculation method of normalized pattern function of field intensity. Secondly the analysis formula of the direct radiation field, reflecting field and diffraction field, as well as the calculation method of reflect point and diffract point are discussed in details. The estimate calculation method of the protection distance between emitting tower and buildings is introduced. Based on the characteristics of antenna and accessories of the broadcast television emitting tower, the electromagnetism environment and protect distance in the specified position of the area around emitting tower are forecasted theoretically.On the field measurement of the electromagnetic radiation around the broadcast television emitting tower area, the antenna system of Henan broadcast television emitting tower, especially the seven omni-directional antenna arrays in the388m top of the tower are introduced in details. This project presents the practical measurement method and test instruments, as well as field measured the specified position on the buildings around emitting tower selected by the theory calculation. Using the transmitting frequencies of the emitting tower, the single frequency emission field intensity and the comprehensive field intensity of broadcast television in the specified spot are gained.The final purpose of this project is, comparing the theoretical calculation of broadcast television electromagnetic intensity and field measurement, to find the electromagnetic environment forecasting method around broadcast television emitting tower, to set up a precise and practical electromagnetic environment forecasting mode for the complex building distribution around emitting tower. This study is significant for the electromagnetic environment evaluation for the built and to be built television engineering projects with good social and economic benefits.