MATLAB: About SNR and transmit power

snr psd

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.

Best Answer

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
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