LoRa 信噪比和接收灵敏度 |
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文章目录
前言一、信噪比极限(SNR LIMIT)二、接收灵敏度
前言
介绍信噪比极限和如何计算接收灵敏度。 参考资料:《LoRa信噪比和接收灵敏度》 一、信噪比极限(SNR LIMIT)信噪比极限,也可以理解为最小解调信噪比。即,接收机能够成功解调信号的最小信噪比,低于这个信噪比接收机将无法解调。 下表是不同的扩频因子对应码片数和信噪比极限: SFchips/symbolSNR limit(dB)7128-7.58256-109512-12.5101024-15112048-17.5124096-20SF增加“1”, S N R l i m i t − 2.5 d B {SNR}_{limit}-2.5dB SNRlimit−2.5dB 二、接收灵敏度S = − 174 + 10 × l o g 10 ( B W ) + N F + S N R l i m i t S = -174 + 10\times log_{10}(BW)+NF+SNR_{limit} S=−174+10×log10(BW)+NF+SNRlimit 接收灵敏度单位dBm,BW单位是Hz,接收机噪声系数(NF)单位是dB,且NF只受硬件性能影响。SX1272和SX1276的NF=6dB 举例:BW=125kHz,NF=6dB,SF7~12S F = 7 : S N R l i m i t = − 7.5 d B SF = 7:SNR_{limit}=-7.5dB SF=7:SNRlimit=−7.5dB S = − 174 + 10 × l o g 10 125000 + 6 − 7.5 = − 125 d B m S = -174 + 10\times log_{10}{125000} + 6 - 7.5 = -125 dBm S=−174+10×log10125000+6−7.5=−125dBm S F = 8 : S N R l i m i t = − 10 d B SF = 8:SNR_{limit}=-10dB SF=8:SNRlimit=−10dB S = − 174 + 10 × l o g 10 125000 + 6 − 10 = − 127 d B m S = -174 + 10\times log_{10}{125000} + 6 -10 = -127dBm S=−174+10×log10125000+6−10=−127dBm S F = 9 : S N R l i m i t = − 12.5 d B SF = 9:SNR_{limit}=-12.5dB SF=9:SNRlimit=−12.5dB S = − 174 + 10 × l o g 10 125000 + 6 − 12.5 = − 130 d B m S = -174 + 10\times log_{10}{125000} + 6 -12.5 = -130dBm S=−174+10×log10125000+6−12.5=−130dBm S F = 10 : S N R l i m i t = − 15 d B SF = 10:SNR_{limit}=-15dB SF=10:SNRlimit=−15dB S = − 174 + 10 × l o g 10 125000 + 6 − 15 = − 132 d B m S = -174 + 10\times log_{10}{125000} + 6 -15 = -132dBm S=−174+10×log10125000+6−15=−132dBm S F = 11 : S N R l i m i t = − 17.5 d B SF = 11:SNR_{limit}=-17.5dB SF=11:SNRlimit=−17.5dB S = − 174 + 10 × l o g 10 125000 + 6 − 17.5 = − 135 d B m S = -174 + 10\times log_{10}{125000} + 6 -17.5 = -135dBm S=−174+10×log10125000+6−17.5=−135dBm S F = 12 : S N R l i m i t = − 20 d B SF = 12:SNR_{limit}=-20dB SF=12:SNRlimit=−20dB S = − 174 + 10 × l o g 10 125000 + 6 − 20 = − 137 d B m S = -174 + 10\times log_{10}{125000} + 6 -20 = -137dBm S=−174+10×log10125000+6−20=−137dBm
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