Assuming a matched situation with lossless interconnections and all at ‘room’ temperature such that kTB = -174 dBm/Hz, there are a few accepted facts.

▪ The noise figure of an attenuator is the same as the attenuation, thus for an example 10 dB attenuator, NF = 10 dB, loss L = 10 dB, and “gain” G = 0.1 (linear factor)

Considering signal output from the attenuator vs. signal input: SO = SI – L or SO = G * SI

▪ Attenuators attenuate noise as well as signals. For the 10 dB attenuator example:

If SI = -100 dBm, then SO = -110 dBm and If NI = -120 dBm/Hz, then NO = -130 dBm/Hz

▪ Attenuators do not attenuate noise to below kTB. Therefore, if the input to an attenuator is at -174 dBm/Hz, the output is also at -174 dBm/Hz

Now for the question and the reason for this topic: Again, for the 10 dB attenuator example, if NI = -164 dBm/Hz, what is NO =