Ku波段卫星通信雨衰计算及分析外文翻译

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1、 Ku波段卫星通信雨衰计算及分析 徐慨、向顺祥、黄林书 电子工程系 海军工程大学 中国武汉 摘要：使用雨量计、频谱分析仪和其他设备，根据模拟结果，测量和分析了武汉市降雨率及雨衰对Ku波段卫星通信信号的影响。分析了降雨率和雨衰的关系，并将结果与国际电信联盟无线电通信部门（ ITU-R） 估计值进行了比较，分析了实际测量值与预测值之间的不同之处。利用测得的数据，对不准确的预测模型，提出了一个改进算法，证明 ITU-R提出的预测模型是正确的。实验结果表明，有必要通过长时间的测量，获得足够的数据，来确定不同站点雨衰与降雨率之间关系。 关键词：频谱分析仪、卫星通信、雨衰、预测模型I 引言在卫星通信链路设

2、计，必须计算链路的效率和冗余。因为信号可能会被吸收和过滤，所以必须提供冗余或一些对抗措施，如自适应功率控制，通过分集接收来提高链路效率。然后有两个问题：应该提供多少冗余来满足链路的有效性要求；应采取什么措施来对抗雨衰。虽然国内外已经做了许多理论的实验研究，但是对于不同的地域链路的设计要求，实验结果不是很符合。在论文中，通过一段时间测量武汉的降雨以及Ku波段卫星信号衰减，绘制了降雨和信号衰减之间的关系图。在比较获得的关系图和ITU-R给出的模型曲线后，证明ITU-R预测模型在不同地区之间存在一些错误，因此有必要进行一些测试，对ITU-R预测模型做一些修改。II 测量系统的原理 图一显示了测量系统

3、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),并发送数据在计算机中的数据

4、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，吸收衰减在慢衰减

5、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，恰好信号衰减发生在那个时候

6、（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况有很大不同，并

7、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，利用相关设备测量了降雨量和

8、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波段卫星通信重要

9、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. On Mic

10、rowave 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,Geneva,200

11、3.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 gauge, spec

12、trum 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 compared with

13、 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 forecasting model

14、 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 satellite

15、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 are two

16、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 so satisf

17、ied 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 and the

18、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 of the

19、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:0.6m; LNB

20、 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 rainfal

21、l 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 data collec

22、tor. When the data are multiplied by 60, then the rainfall of that hour is got（mm/h）.Testing place: Wuhan; latitude:30.52；longitude114.31 ； altitude ： 23.3m ； testing frequency ：12.333GHz； elevation of the antenna：48.45。 Fig.1 Experimental system structureIII. TESTING RESULT AND MODELING ANALYSISA.

23、ITU-R rainfall attenuation model6 A =gL （dB） （1） g = aRb （dB/km） （2） 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 referenc

24、ed level in sunshine The change of absorbance 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 im

25、portant factors among slow change attenuations.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 ra

26、in attenuation To take the average of the 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,

27、r A is the signal level per minute in rain.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.

28、3. Compared the two graphs, these conclusion 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

29、 are not only happen during the rain time, 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 i

30、s relative with the period which the rainfall 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 rel

31、ationship between the rain attenuation and 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 draw

32、n 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 att

33、enuation model from ITU-R , it is defined as: Ap=Aitu-rPerror （4） Where, P A is the rain attenuation after compensating, ITU R A - is the forecasted attenuation from the ITU-R model, error P isthe compensating factor. Fig.5 is the error curve. “*”is the error valueprovided by the result of fig.4 and

34、 curve is drawn up by the method of Least Squares Algorithm, the expression is: Perror=-0.0006*R*R+0.1308*R-0.1847 (dB) Where , R is the rainfall. Then the modified rainfall forecasting model is: Ap=Aitu-r(-0.0006*R*R+0.1308*R-0.1847 ) Fig 4 Relationship between the rain attenuation Fig 5. The error

35、 curve.V. CONCLUSION In this paper, the rainfall and Ku-band satellite signal attenuation are measured by using the equipments. And then the measured value is compared with the rainfall model provided by the ITU-R and some differences are found between the measured and forecasted. We propose a modif

36、ied algorithm to modify the model provided by ITU-R by analyzing the measured data. The result shows that after modifying data will be more consistent with the real value with theincreasing of the measured data number. Signal attenuation is related with the rainfall lasting period. For the same rain

37、fall ratio, the signal attenuation caused by rainfall lasting for 20 minutes is greater then the one for one or two minutes. Meanwhile ,the real situation is very complex and various, especially some factors decided the rain attenuation ,such as the dimension of raindrop, the rainfall distributing o

38、n the whole attenuation path, wind velocity and temperature ,they are all even. Then it is necessary for us to set up a long-time observation mechanism to obtain enough data about rainfall attenuation and rainfall. These data will be the important foundation in the research for the Ka-band satellite

39、 communication in the future.REFERENCES1Zulfajri B H, Kiyotaka F, Kenichi I, and Mitsuo T.Measurement of Ku-Band Rain Attenuation Using Several VSATs in Kyushu Island,JapanJ. IEEE Antennas and Wireless Propagation Letters, 2002(1): 116-119.2J.Kang,H.Echigo,K.Ohnuma,S.Nishida,and R.Sato,”Three-year m

40、easurement by VSAT system and CCIR estimation for rain attenuation in Ku-band satellite channel, ”IEICE Trans.Commun.,vol.E79-B,pp.1546-1558, Oct.1997.3Amaya C, Rogers D V. Characteristics of Rain Fading on Ka-Band SatelliteEarth Links in a Pacific Maritime ClimateJ. IEEE Trans. On Microwave Theory

41、and Techniques, 2002, 50(1): 41-45.4 Dissanayake A, Allnuh J. A Prediction Model that RainAttenuation and other Propagation Impairments alongEarth-Satellite PathJ. IEEE Trans. On Antennas andPropagation, 1997, 45(10): 1546-1557.5 Dong You Choi,Rain attenuation prediction model by using the 1-hour ra

42、in rate without 1-minute rain rate conversionJ.IJCSNS International Journal of Computer Science and Network Security,2006(6):130-133.6 Rec.ITU-R PN.618-8,Propagation data and prediction methods required for the design of earth-space telecommunications systemsS.ITU,Geneva,2003. Author: Xu Kai(M90-) was born in 1965,in Jiangsu, China. He became an associate-Professor in 2001.His interests include wave propagation, scattering and satellite communication system.1097