about SNR and transmit power

Question

CorneCap 2014-3-17

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https://ww2.mathworks.cn/matlabcentral/answers/121939-about-snr-and-transmit-power

回答： CorneCap 2014-4-10

Hello everyone, i m trying to calculate SNR for PLC direct link. it's given that SNR=transmit power spectral density* signal power attenuation /noise PSD.

So when applying, it's said : The total transmit power is chosen to be 12.5 dbmw with the average PSD -60 dbmw/Hz over the signal frequency band 2-20 Mhz.

i want to know which value of the power transmit should i take to calculate SNR(12.5 or -60)? i have already found the signal attenuation and noise PSD (depending on frequency). any help will be appreciated.

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Answer 1

Honglei Chen 2014-3-17

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https://ww2.mathworks.cn/matlabcentral/answers/121939-about-snr-and-transmit-power#answer_128816

If you want to use power spectral density, you should use the quantity corresponds to -60. Note that this is measured in dB. Since your formula involves division, you need to translate it to linear scale, which is 1e-6.

FYI, -60 and 12.5 is related. For -60dBmw/Hz over a 18 MHz band (20MHz - 2MHz), the power is actually 1e-6*18e6 = 18 mw. If you translate 18 mw to dB, you get 12.5 dBmw.

HTH