Variables
Description
What is this formula?
Noise Figure (NF) quantifies how much a communication device degrades the signal-to-noise ratio as a signal passes through it. It compares the input SNR to the output SNR.
When to use it
Use this formula when evaluating amplifiers, receivers, low-noise amplifiers (LNAs), communication equipment, and RF systems where noise performance is critical.
Example
An amplifier receives a signal with an input SNR of 1000 and delivers an output SNR of 250.
Formula:
NF = (Si/Ni)/(So/No)
Substitution:
NF = 1000/250
Result:
NF = 4
NF = 6.02 dB
Applications
RF amplifiers, satellite receivers, radio astronomy, wireless communication systems, microwave links, receiver design, and telecommunications testing.
Note
Noise Figure is typically reported in decibels using NFdB = 10·log10(NF). An ideal noiseless device has NF = 1 (0 dB). Real devices always introduce additional noise, causing NF to exceed unity. Different measurement methods and reference temperatures may lead to slight variations in reported values.