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卫星下行链路降雨除了导致信号受到衰减外,还会升高卫星地面接收机的噪声温度,从而进一步恶化卫星信道的通信质量、本文就下行链路雨衰对卫星地面接收系统噪声的影响进行了研究,并基于ITU—R推荐的降雨衰减预测模型,对一个实例进行了仿真、分析,得到了雨中噪声温度、噪声功率与极化方式、工作频率、接收天线仰角、降雨强度之间的变化关系. 相似文献
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面板缝隙会引起天线增益的下降和噪声温度的提高,对追求极致灵敏度的射电望远镜而言,其影响不可忽略。针对国际大科学工程平方公里阵(SKA)的核心设备——15 m双偏置格里高利天线,结合具体的结构设计和制造工艺,对副反射面缝隙的影响进行分析。通过电磁分析指导结构设计,有效抑制了面板缝隙对天线灵敏度的影响,保证了SKA天线的性能。 相似文献
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噪声系数是衡量一个小信号处理系统噪声性能的重要参数,噪声系数测量对于设计控制系统噪声具有重要的指导作用。该文首先介绍了噪声系数的相关基本概念,接着重点详细描述了噪声系数的Y因数测量方法,并针对如何提高测量的精度,讨论了测量时应注意的相关问题。 相似文献
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Early warning signals of abrupt temperature change in different regions of China over the past 50 years
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In this paper, the early warning signals of abrupt temperature change in different regions of China are investigated. Seven regions are divided on the basis of different climate temperature patterns, obtained through the rotated empirical orthogonal function, and the signal-to-noise temperature ratios for each region are then calculated. Based on the concept of critical slowing down, the temperature data that contain noise in the different regions of China are preprocessed to study the early warning signals of abrupt climate change. First, the Mann-Kendall method is used to identify the instant of abrupt climate change in the temperature data. Second, autocorrelation coefficients that can identify critical slowing down are calculated. The results show that the critical slowing down phenomenon appeared in temperature data about 5-10 years before abrupt climate change occurred, which indicates that the critical slowing down phenomenon is a possible early warning signal for abrupt climate change, and that noise has less influence on the detection results of the early warning signals. Accordingly, this demonstrates that the model is reliable in identifying the early warning signals of abrupt climate change based on detecting the critical slowing down phenomenon, which provides an experimental basis for the actual application of the method. 相似文献
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作为卫星接收系统的接收端和信号源 ,高频头的重要性毋庸置疑。存在的问题主要反映在工作性能不稳定 ,如本振频率漂移、热稳定性差、频段的一致性差、增益低、甚至收不到等等 ,所以安装调试卫星电视接收系统要懂得对所配高频头进行正确的选择、安装与维护。 相似文献
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