The Research On The Law Of Wierless Sensor Signal Propagation In The Circular Sewer

With the attention of China and the world on environmental issues, the new flowmeter has constantly being designed, and urgently being put into use.Therefore, studying the principle of wireless signal transmission in the sewer has great theoretical and practical value.Purpose of this paper is how to transport the sensor signals accurately through the sewers,providing the theoretical basis for the open channel flowmeter to put into use. Therefore,in this paper,the in-depth and detailed research has been carried on about the propagation of the wireless signal in the sewer,and a number of innovative achievements have been made. The work and main contents are as follows:For such a complex limited space, based on the full analysis of the various factors affecting the transmission signal in the sewer,the hybrid method is proposed to describe the wireless signal propagation within the sewer and a wireless channel hybrid model is also established.The paper mainly discusses the general laws of the electromagnetic wave propagation, focusing on the propagation characteristics of electromagnetic waves in the circular tunnel, and then a detailed analysis has been done on the wireless transmission characteristics in the circular sewers,and finally,the hybrid model is builded.Because of the complex environment within the sewer,it is essential to study various factors on the impact of signal transmission.According to the actual situation in the sewer,it is focused on exploring the impact of the wet wall and water vapor on the signal attenuation rate. the conclusions are as follows: The attenuation rate becomes smaller when the frequency gets higher;the increase of the radius is propitious to guide the wave propagation; the bend, tilt and branches of the sewer will increase the wireless transmission attenuation; and if the water vapor with higher density, the attenuation rate is proved to be more greater; in addition,the wet wall of sewer will cause changes in electrical parameters.Through systematic analysis of various factors on the effect of transmission characteristics, the hybrid model has been proposed to predict the law of signal wireless transmission,and then,the space of the sewer is divided into the near field area and the distant field area at two different regions: in the near-field zone, the free space propagation model could be used to predict propagation loss;while in the far-field zone, the modified waveguide propagation model could be used.Previous waveguide theory is used for the wireless transmission tunnel, but now,this method is used to study the signal wireless transmission characteristics in the sewer, and the hybrid model is creatively proposed to establish wireless channel model.In particular, the special factors affecting to the signal----the water is taken into account, and cleverly integrated into the model which makes the model more complete and realistic. In the later experiment, it is also proved that the model has good practical value.