Research On Characteristic Of Satellite Communication Link Ku Band

Satellite communication system has experienced rapid development for its unique advantage and has become an essential part of telecommunication in the future. However, in the process of satellite communication, the electric wave transmission is affected by many factors in the link of transmission, for example transmission attenuation, the attenuation of free space,rainfall,snowfall will bring the attenuation of different level. The rainfall affects the signal more and will lead to the destroy of the link of the satellite communication. Especially to the satellite link system of Ku band(14/12GHz) and above, the destroy of rainfall to the signal is heavier because of the high frequency. The rainfall is one of the main reasons that affect the validity and the dependability of the satellite communication system. Therefore, in order to ensure the transmission quality, reliability and economical efficiency, we must master the rainfall attenuation influence of earth station setting areas accurately while the designing the earth-space satellite communication link.Because the rainfall characteristic and attenuation of rainfall have strong characteristic regionally, different geographical and climatic there is difference. We have to test in the different area for a long time to get the accurate rainfall attenuation characteristic. Among the different test methods, the method that receiving the satellite signal can realize the test more accurately. The research of this aspect is very lack in the present of our country and there is a long distance from the developed countries, so it is necessary to develop the research.The long time observation of the satellite signal is necessary for researching the effect of rainfall to the transmission quality of the satellite link. To study the characteristic of the long time and short time internal about the satellite signal and master the change disciplinarian of rainfall attenuation by trial in order to realizethe useful compensation. In order to prevent and decrease the influence of all factors to satellite link, we need to know and master the transmission characteristic of satellite link. In order to master the transmission characteristic of satellite link, and study the effect of rainfall to satellite link, we designed and realized the Automatic observation system of satellite link of Ku band. The system utilizes GP-IB interface technology in stead of the usually manual test to realize the computer controls the spectrum analyzer and decreases the test error caused by man_made. At the same time, through the test programme, we realize the automatic test which increases the validity and veracity. I developed the test programme by Visual Basic whose plenty of interfaces make the user's operation easier. The test software has a high automatic level and can realize the long time, short time interval test automaticly. We research the change of satellite beaconing by observing the beaconing's level of Asia Sat-3S(105.5E) Satellite consecutively, and get the change of signal attenuation caused by rainfall. This can provide gist for realizing the system design and attenuation compensation better. The time internal of receiving data this system is 1s,and the short time interval data provide the advantage for study the satellite link character more accurately. Furthermore, we observe sun outage phenomenon by this system successfully.From the beginning of June 2005,the system has observed the sat-3s for almost 2 years continually and receives plenty of real data including the rainfall attenuation, snow attenuation, sun outage which provide the real and dependably data source for researching the satellite link characteristic. By concluding and analyzing the data, i study the disciplinarian and to find the useful compensation method in order to decrease or cancel the break to the satellite link.This paper makes an introduction of the basic knowledge of satellitecommunication and the factors that affect the link transmission of satellite communication. I introduces the effect that rainfall to communication link of satellite stressly. Then i introduces the present study status of rain attenuation home, physical characters of the rainfall and bring one wide application rain attenuation prediction method: ITU-R prediction method. In order to decrease the effect that rainfall to satellite link, we introduce several typical compensation methods. We designed and realized the automatic observation system of satellite link and received the real data. In the automatic observation system, we utilized GP-IB interface technology in stead of the usually manual test and realized the operation and control that computer to intelligent test instrument which decrease the test error caused by man_made. Further, we anglicized the rain attenuation character of Ku band satellite communication system, with combination of the geographical and climatic distribution, and we obtain some useful results: The primary rain attenuation influence factor is the minute rainfall rate of 0.01% time. From the contour map of minute rainfall rate, we can see that, the heavy rainfall areas are coincident with serious rain attenuation areas. The main work of this paper is dealing with and analyzing the real data received this two year, studying the character of rainfall attenuation Ku band, confirming the rainfall character of satellite communication system of Ku band this area, and we find some disciplinarian and commonness. The result accords with the prediction method of ITU-R and validate the validity of ITU-R prediction method in Chang Chun.