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所在平台: Udemy |
课程主页: https://www.udemy.com/course/propagation-effects-on-satellite-communication/
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课程名称：卫星通信中的传播效应 课程概述：本课程主要介绍大气吸收、云衰减、对流层和离子层闪烁以及低角度衰落、雨引起的衰减和雨引起的交叉极化干扰等内容。卫星与地球站之间的信号在传输过程中必须穿过地球的大气层，包括离子层。在大气中，信号能量因大气气体的存在而被吸收，这种损失称为大气吸收。在信号从地球站传输到卫星的过程中，会发生多种损失，这些损失会因天气状况的不同而有所变化，因此与天气相关的损失被称为大气损失。另一类损失是离子层损失。当无线电波在卫星和地球站之间传播时，也要穿过离子层。离子层是地球大气的上层，主要受到太阳辐射的影响而被电离，白天的高度与夜晚有所不同，夜间由于没有太阳辐射而变化。在离子层中，自由电子并非均匀分布，而是形成不同的层次。信号穿过离子层会导致信号的波动，效果包括闪烁、吸收、到达方向变化、传播延迟、色散、频率变化和极化旋转等。通过提高信号频率，可以减少这些影响。 课程大纲：无
This course consist of introduction to atmospheric absorption, cloud attenuation, tropospheric and ionospeheric scintillation and low angle fading, rain induced attenuation, rain induced cross polarization interference. As we know that, a signal traveling between an earth station and a satellite must pass through the earth's atmosphere, including the ionosphere. The signal energy is absorbed in earth's atmosphere due to presence of atmospheric gases. These loss is called as atmospheric absorption. There are various losses occurs at signal transition from earth station to satellite. These losses are varying as per the weather condition. Therefor the losses occurs due to weather related losses are referred as atmospheric losses.Another term losses due to ionosphere losses. When the radio waves traveling between satellites and earth stations must pass through the ionosphere. The ionosphere is the upper region of the earth's atmosphere, which has been ionized, mainly by solar radiation, in day it has different height from surface of earth and in night it changes due to no solar radiation.. In ionosphere the free electrons are not uniformly distributed but form in layers. The signal passes through the ionosphere gives rise to fluctuations in signal that effects include scintillation, absorption, variation in the direction of arrival, propagation delay, dispersion, frequency change, and polarization rotation. All these effects can be minimized by increasing the signal frequency.
