What is Noise Figure?

In a receiver system, the noise added by the system components degrades the received signal, which impacts the performance of the whole system. Noise figure is the measure of degradation caused by the components of the system. Lower the value of NF better is the performance of the system.

The Noise Figure can be calculated by expressing noise factor in decibels (dB).

Noise Factor is the measure of degradation of the signal to noise ratio in a device. It is the ratio of the Signal to Noise Ratio at the input to the Signal to Noise Ratio at the output. Since the signal to noise ratio at the output will always be lower than the Signal to Noise ratio at the input, the Noise Factor is always less than 1. The Lower Noise Factors results in better performance of a devices.

Where, 

S_in = Signal level at input

N_in = Noise level at input

S_out = Signal level at output

N_out = Noise level at output