Noise Power Calculations in dB or dBm

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dBm is a unit of power (dB referenced to 1 mW)
dB is a (dimensionless) ratio (value/reference in dB).

Hence, if you want noise power you need to use dBm.
All you need is 10log10 (P/P0) where P is the power and P0 is 1 mW.

f95toli Recognitions: Gold Member Science Advisor	dBm is a unit of power (dB referenced to 1 mW) dB is a (dimensionless) ratio (value/reference in dB). Hence, if you want noise power you need to use dBm. All you need is 10log10 (P/P0) where P is the power and P0 is 1 mW.