Converting to dBm from pwelch function

Asked by Divya Venkatesha on 31 Jul 2013 at 10:34
Latest activity Commented on by Wayne King about 8 hours ago

How do I convert Pxx that I get from using the pwelch to dBm. I know we can convert to dB by 10*log10(Pxx) but I was unsure how we would do it to get dBm.

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Divya Venkatesha

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Answer by Wayne King on 31 Jul 2013 at 11:12
Edited by Wayne King on 31 Jul 2013 at 11:13

Since 1 milliwatt is 0 dBm, you can do the following:

 10*log10(1e3*Pxx)

from the above, you see that a power of 1 milliwatt will equal 0 dBm.

or equivalently,

10*log10(Pxx)+30

2 Comments

Divya Venkatesha about 8 hours ago

Hi Wayne,

Thanks for your reply. I tried that and it doesnt seem to stack up. I have an input power level of -80 and if I add 30 to the 10log10(Pxx) I get 71dB which gives me a gain of 151dB. But I have tried using voltages and the gain should be 75dB which is also verified by simulations. So I am really not sure what units Pxx has. Any feed back will be appreciated.

Many Thanks Divya

Wayne King about 8 hours ago

What units is your input time series in?

Wayne King

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