链路预算公式与说明.doc

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1、卫星通信技术联盟：62407999★★★★表示10LogX斜体表示10X/10c=2.998e8光速Re=6371km地球赤道半径h=35793km卫星离地面高度K=1.38×10-23J/K波尔兹曼常数4π/(c/f)2为单位面积理想天线增益G0Noise(K)=290×[Noise(dB)-1]D=天线与卫星的距离Freespaceloss=32.4+20Log(D×f)自由空间传输损耗（注：D单位km；f单位MHz）Symbolrate=Daterate/（M×FECcoderate）符号率(MBaud)Occupiedbandwidth=Symbolrate×Spreadfactor

2、占用带宽(MHz)Spreadfactor=1.2Noisebandwidth=Occupiedbandwidth×106噪声带宽(dB.Hz)Allocatedtransponderbandwidth=(Symbolrate×Carrierspacingfactor)+Bandwidthallocationstepsize转发器分配带宽(MHz)上行链路功放功率与天线选择：EIRPUS=FreespacelossU+AtmosphericabsorptionU+TroposphericscintillationfadingU+MispointlossU+SFD-4π/(c/f)2上行饱和等

3、效全向辐射功率dBWEIPRU=EIRPUS-IBO-Transponderbandwidth/Allocatedtransponderbandwidth载波在卫星天线口面上的通量密度dBW(PFD)RequiredHPApowercapability=TotalHPApowerrequired=EIRPU-Antennagain-(Couplingloss)U所需功放功率W（也可以固定功率来确定天线尺寸）(C/N0)U=EIRPU-(FreespacelossU+AtmosphericabsorptionU+TroposphericscintillationfadingU+Mispoint

4、lossU)-K+(G/T)S(C/N)U=(C/N0)U-Noisebandwidth=SFD-4π/(c/f)2-IBO-Transponderbandwidth/Allocatedtransponderbandwidth-K+(G/T)S-NoisebandwidthAntennaefficiency=Antennagain×c2/(πRf)2天线增益效率（注：c单位m；f单位Hz；R单位m）卫星通信技术联盟：62407999★★★★Antennanoise==以波长为单位，天线有效面积为权重的亮温度对全天空的积分≈15×Antennaefficiency+(1-Antennaeffi

5、ciency)×[15×sinθ/(cosθ+sinθ)+(140+θ)×cosθ/(cosθ+sinθ)]θ为天线仰角在（0，90）G/T=Antennagain-Antennanoise+290×(CouplinglossD-1)+290×(LNBnoisefigure-1)×CouplinglossD(G/T)I=Antennagain-Antennanoise+290×(CouplinglossD-1)+290×(LNBnoisefigure-1)×CouplinglossD+[290×CouplinglossD×(RXL-1)]/GLNB+CouplinglossD×RXL×TRX

6、/GLNB接收线缆与接收机引入的噪声（TRX为接收机的噪声）EIRPD=EIRPS-OBO-Transponderbandwidth/Allocatedtransponderbandwidth(C/No)D=EIRPD–(FreespacelossD+AtmosphericabsorptionD+TroposphericscintillationfadingD+MispointlossD)-K+G/T(C/N)D=(C/No)D-Noisebandwidth=EIRPD–(FreespacelossD+AtmosphericabsorptionD+Troposphericscintillat

7、ionfadingD+MispointlossD)-K+G/T-NoisebandwidthC/(N+I)=C/(N+I)=C/(No+Io)-NoisebandwidthEb/(No+Io)=[C/(N+I)+1-1]/[（FECcoderate×Log2M）/Spreadfactor]=[C/(N+I)+1-1]/Daterate/Occupiedbandwidth频谱仪读到的MARKEDELTA=C/(