The Measure Method Research Of Equivalent Electrical Parameters Of Building

With the national emphasis on the environmental cause, the problem of electromagnetic radiation becomes more and more serious. Electromagnetic radiation prediction system is one hot research. When forecasting the radiation of devices built in urban district, such as high tension line, communication base station, radio and television towers and so, we need to consider the affection of constructions on electromagnetic wave propagation, because path and gain/phase of electromagnetic wave may be changed by constructions. Propagation paths change is mainly caused by reflection and diffraction, and gain/phase change is mainly caused by dielectric property. It can lead to loss of the spreading electromagnetic signals. It is most important to study the equivalent electrical parameters of constructions based on above reasons.The main content of this article is built on the basis of researching equivalent electrical parameters of the building. Firstly, we determine the main test frequencies and objects by analyzing the causes of hindering the radiation signal propagation and the sources of electromagnetic radiation signals. The most main radiation source is electromagnetic waves of communication base stations, whose frequency range is between 800MHz and 2.1 GHz. By referring to lots of data, we find that the method of measuring equivalent circuit parameters is usually coaxial transmission/reflection method. But the coaxial probe method and the free space method is more suitable for characteristics of the building.We give the detail explanation about testing theory and calibration process of the two methods in this paper. The theoretical principle of coaxial probe method is based on quasi-static model, which omits repeatedly mode. And the theoretical principle of free space method is based on Fresnel law of reflection, which inverses equivalent electrical parameters of materials easily after using Metal plate calibration. From the differences between two methods, we know that the probe method is used in laboratory, which is decided by the process of calibration. And the free space method has advantage in the field tests. After using the free space method to measure two tall building walls, we find the data from the two methods is similar as theoretical value. Moreover the data of equivalent conductivity can be changed into versus frequency curve by curve fitting. This is good for set up the data of equivalent conductivity in electromagnetic radiation prediction system.