Noise Factor: Noise Factor is a measure of how much signal to noise ratio (SNR) gets degraded by the RF system block. In the electronic systems at the given temperature, due to random thermal motion the SNR at the output will always be lower than the SNR at the input. Thus, the Noise Factor is always greater than unity provided measurement bandwidth is same for input and output. Noise factor of lossy network / attenuator is equal to the power loss. For example, a 3 dB RF attenuator increases noise factor by 2 (since, \(10^{\frac{3\,dB}{10}}=2\))
Noise Figure: Noise Figure is obtained from Noise Factor by
\(Noise \, Figure = 10*log10(Noise \, Factor)\, dB \)
Noise Figure is commonly used to specify the performance of RF receiver (especially Low Noise Amplifers). Lower the Noise Figure better the performance of RF receiver.
\(Noise \, Factor = \frac{\frac{S_{in}}{N_{in}}}{\frac{S_{out}}{N_{out}}} \)
\(Noise \, Figure = 10*log10(Noise \, Factor)\, dB \)
| Where: |
| \(S_{in} \) = Signal Level at Input |
| \(N_{in} \) = Noise Level at Input |
| \(S_{in} \) = Signal Level at Output |
| \(N_{in} \) = Noise Level at Output |