Ku波段卫星通信雨衰计算及分析外文翻译文档格式.docx

1、 图一显示了测量系统的原理。该图的左侧的是降雨衰耗估算 。下行链路信号由天线接收，并且其频率被转增下来的低噪声B转换，并且随后转到频谱。最后，通过RS-232接口，信号电压被保存到计算机。菱形天线 :0.6m，LNB振荡器频率 11300MHz ；输入频率：12.25GHZ12.75GHZ；输出频率：950MHZ1450MHZ；因为它是垂直极化测量信号,电源电路是采用12.5 V直流 ；光谱频率范围:3KHZ 3GHZ,10个值是每分钟收集。 右侧是降雨量的测量。这个雨量计的测量精度:0.1毫米 7毫米/小时,运行电压:9 24 v直流电源提供的收集器.雨量计得到了降雨的每分钟（毫米）,并发送

2、数据在计算机中的数据收集器。当数据乘以60,那么降雨的小时是有（毫米/小时）。测试地点：武汉，纬度:30.52；经度：114.31高度：23.3米测试频率：12.333GHz;仰角的天线：48.45。 Fig.1 实验系统结构图III 测试结果及建模分析A. ITU-R降雨衰减模型 A =gL （dB） （1） g = aRb （dB/km） （2） 其中，L是降雨的有效路径， g是降雨衰减比， R是雨量比， a，b是相关系数，其值随频率不同变化。B.阳光下计算放的信号的参考电平吸光度的衰减在雨天、云和大气的变化是缓慢的。大气吸收有氧气和水蒸气组成。其中水的蒸气在不同的天气变化最大。相比较而言

3、，吸收衰减在慢衰减中是最主要的因素。为了去除噪声和闪烁的影响，分析了在下雨之前三天和下雨之后三天的晴朗天气所有的信号电平，得到了晴朗天气的信号参考电平As。C.计算雨衰取在1分钟内获得的10个信号得平均值,就得到了雨中每分钟的信号电平。然后每分钟雨衰如下： A = As - Ar （dB）其中，A是指雨衰，As是晴朗天气的信号参考电平，Ar是雨中的每分钟信号电平。D.测量结果分析 图2表示的是武汉地区2008-05-03 的降雨情况。水平轴是时间,垂直是雨衰减率。信号随时间衰减如图3所示。比较两个图，可以得出以下结论：（1）降雨越大，雨衰也越大。最大的降雨发生在5月3号的21:00，恰好信号衰

4、减发生在那个时候 （2）信号衰减是不仅发生在下雨的时候，下雨后也有，因为在某些方面天空中的云也使信号发生衰减。例如，5月3日在17:00-18:00，虽然不下雨，但很明显，仍然有信号衰减。（3）雨衰减率期间的降雨量是相对持久。在相同的降雨，信号由降雨引起的为20的衰减分钟显然是大于一个或两分钟。 Fig2. 武汉降雨环境 Fig 3 信号衰减E.误差分析雨衰减和信号衰减之间的关系如图4所示。水平轴是降雨,垂直轴的是雨衰减率。“*”曲线是降雨试验测得,“”曲线是在ITU-R提供的公式模型的基础上绘制。“”曲线是草拟的测量值处理的最小二乘方法算法。如图所示,由ITU-R提供雨衰模型与武汉地区实际情

5、况有很大不同，并且随着降雨量的增加误差也增大。 图4：雨衰之间的关系 Fig 5. 误差曲线 IV 改进后的算法模型 修改后的ITU-R雨衰模型： Ap=Aitu-rPerror其中,Ap是修正后的雨衰减，Aitu-r是ITU-R雨衰模型预测的雨衰，Perror是修正因子。 图5是误差曲线。“*”是图4所提供的误差值曲线，曲线是由最小二乘法得到的。表达式为： Perror=-0.0006*R*R+0.1308*R-0.1847 （dB）其中，R是降雨量。则修改后的预测模型是:Ap=Aitu-r（-0.0006*R*R+0.1308*R-0.1847 ） （dB）V. 结论 在本文中，利用相关设

6、备测量了降雨量和Ku波段卫星通信信号衰减的值。通过比较测量值和ITU-R提供的雨衰模型，发现了测量值和预测值之间的一些不同。通过分析测量数据，提出了一个修改算法来修正ITU-R提供的雨衰模型。结果表明，随着测得的数据的数量的增加这个修改后的数据会与实际值更吻合。 信号衰减与降雨持续时间有关。同样的降雨比,持续20分钟降雨引起的信号衰减比续1分钟或2分钟降雨大得多。与此同时,真正的情况是非常复杂的、多方面的，特别是决定雨衰减一些因素,如雨滴的大小,降水在整个衰减路径的分布、风速和温度，他们都对雨衰有影响。所以我们应该建立一个长期的观察机制，来获得降雨衰减和降雨的足够数据。这些数据将是未来研究ka

7、波段卫星通信重要的基础。参考文献 1 Zulfajri B H，Kiyotaka F, Kenichi I, and Mitsuo T。日本九州岛Ku波段雨衰测量， J 。IEEE天线与无线传播快报，2002（1）：116-119.。2 J.Kang，H.Echigo K.Ohnuma，S.Nishida，R.Sato，“VSAT系统三年测量和在Ku波段雨衰卫星通道CCIR估计”，IEICE Trans.Commun，vol.E79-B，pp.1546-1558，1997年10月。3Amaya C, Rogers D V亚太海事展气候变化Ka波段卫星地球链接降雨衰减特性J。IEEE Trans

8、. On Microwave Theory andTechniques, 2002, 50（1）: 41-454 Dissanayake A, Allnuh J.雨衰减和其他传播障碍以及地球卫星路径的预测模型J.IEEE Trans. On Antennas andPropagation, 1997, 45（10）: 1546-1557.5 Dong You Choi，使用1小时降雨率无1分钟降雨率转换的雨衰预测模型J。IJCSN计算机科学国际期刊和网络安全报,2006（6）:130-1336 Rec.ITU-R PN.618-8，地球电信系统空间设计方法需要传播数据和预测方法S.ITU,Ge

9、neva,2003.作者：许凯（M90）出生于1965年，江苏，中国。他在2001年成为联营公司教授。他的兴趣包括波的传播，散射和卫星通信系统。外文原文： Measuring and Analyzer of Rain Attenuation for Satellite Communication in Ku band XU kai, Xiang shunxiang, Huang Linshu Electronics Engineering Department, Naval Univ. of Engineering , Wu han,China AbstractUsing a rain gau

10、ge, spectrum analyzer and other equipments,rain rate and rain attenuation for the satellite communication signals in Ku band（14/12GHz） in Wuhan city are measured and analyzed simultaneously according to simulations. The relation between rainattenuation and rain rate are analyzed, the result is compa

11、red with the estimated International Telecommunication Union Radio Communication Sector （ITU-R） and the difference between the prediction and the measuration is analyzed. To the inaccuracy of the forecasting model, a modified algorithm is presented and by using the data measured, the ITU-R forecasti

12、ng model is corrected. The experiment results suggest it is necessary to measure for long time to get enough data of the relationbetween rain attenuation and rain rate at differentstations.Keywords：spectrum analyzer; satellite communication; rain attenuation；forecasting modelI. INTRODUCTIONIn the sa

13、tellite communication link designing,efficiency and redundancy of link must be computed.For the signal may be absorbed and glittering ,enough redundancy or some counter-measure must be provided, such as the adaptive power control, receiving by dividing to improve the efficiency of link1. Then there

14、are two problems: how much does the link redundancy should be provided to meet the demand of the efficiency of the link; what kind of counter measure to rain attenuation should be taken. Although many theoretical an experimental study have been done in home or oversea2-5, the results are still not s

15、o satisfied the design demand from various district links.In the paper, by measuring on the rainfall in Wuhan and the satellite signal attenuation of Ku band for a period, the relationship shown in graph between the rainfall and its attenuation are got. After the comparison between the result graph

16、and the modeling curve given by the ITU-R, it is proved that inaccuracy exist in the ITU-R forecasting to the rainfall in various district then it is necessary to take some testing and dosome modification.II. PRINCIPLE OF MEASUREMENT SYSTEM Principle of measurement system is shown in fig.1. The left

17、 of the figure are the rainfall attenuation measurement. The downlink signal is received by the antenna and its frequency are conversed down by theLow Noise B conversion and then goes to the spectrum. At last it saves the signal voltage to the computer through the RS-232 interface. Antenna diamond:0

18、.6m; LNB oscillator frequency: 11300MHz ； input frequency：12.25GHz12.75GHz；output frequency：950MHz1450MHz；since it is the vertical polarized signal measured ,the power supply circuit is adapted the 12.5V DC; the spectrum frequency range :3KHz3GHz， 10 values are collected per minute. The right is the

19、 rainfall measurement. The pluviometers measure precision：0.1mm7mm/h； denotation error ： one-off rainfall 10mm ，error0.2mm，one-off rainfall 10mm，error2%；running voltage：924V DC are provided by the collector. The pluviometer gets the rainfall per minute（mm）and send the data to the computer by the dat

20、a collector. When the data are multiplied by 60, then the rainfall of that hour is got（mm/h）.Testing place: Wuhan; latitude:longitude114.31 ； altitude ： 23.3m ； testing frequency ：12.333GHz； elevation of the antenna： Fig.1 Experimental system structureIII. TESTING RESULT AND MODELING ANALYSISA. ITU-

21、R rainfall attenuation model6 Where, L is the rainfall effective path, g is the ratio of rainfall attenuation , R is the ratio of rainfall, a 、b are correlative coefficient. the value is varied with the different frequency. B. Calculating of the signal referenced level in sunshine The change of abso

22、rbance attenuation of rain, cloud and atmosphere is slow change. Atmosphere absorption are made of oxygen and water vapors, among them the water vapors are varied mostly with the different weather. Taking one with another, absorption attenuation are the most important factors among slow change atten

23、uations.To remove the influence of the noise and scintilla , the mean is got from all the signal levels in sunshine weather in the three days before and after the rain, the signal referenced level in sunshine weather s A is obtained then . C. Calculating the rain attenuation To take the average of t

24、he 10 signal levels which are adapted in one minute, the signal level per minute in rain is obtained .Then the rain attenuation of the minute is got as follows: A = As - Ar （dB） （3）Where, A is the rain attenuation，As is the signal referenced level in sunshine, r A is the signal level per minute in r

25、ain.D. Measuring Result AnalysisIt is shown in figure.2 that the raining circumstance in Wuhan district on 2008-05-03.The horizontal axes is time, the vertical is the rain attenuation ratio. The signal attenuation corresponding with the time is shown in figure.3. Compared the two graphs, these concl

26、usion can be drawn:（1） The heavier is the rainfall, the greater is the corresponding rain attenuation ratio.When the maximum of rainfall happened at about 21:00 hour on May 3rd, the signal attenuation happened just at that time then. （2）.The signal attenuation are not only happen during the rain tim

27、e, but also after the rain, because the cloud in sky also causes theattenuation in some respects. For instance, during 17:00 -18:00 on May 3rd, though there is not rain ,but it is obvious that there is still signal attenuation. （3） The rain attenuation ratio is relative with the period which the rai

28、nfall is lasting. To the same rainfall, the signalattenuation which is caused by the rainfall for 20 minutes is clearly greater than that for one or two minutes. Fig2. Raining circumstance inWuhan Fig 3 Signal attenuation with the timeE. Error analysis The relationship between the rain attenuation a

29、nd the signal rain attenuation is shown in fig.4. The horizontal axes is rainfall, the vertical is the rain attenuation ratio. “*”-curve is the rainfall measured in experiment,“”-curve is drawn based on the formula provided by the ITU-R model. “”-curve is drawn up of measured value processed by the method of Least Squares Algorithm. As shown, the rain attenuation model provided by ITU-R is greatly varied from thereal situation in Wuhan district and the error increases with the rainfalls increasingIV. MODIFIED ALGORITHM TO THE MODEL To modify the rain attenuation model from ITU-