The noise figure (F) of a network is defined as the ratio of the signal-to-noise power ratio at the input to the signal-to-noise power ratio at the output. Thus the noise figure of a network is the decrease or degradation in the signal-to-noise ratio as the signal goes through the network. A low noise figure means that very little noise is added by the network. This paper will walk you through definition and concepts of noise figure and RF and Microwave noise figure measurements (including noise figure and noise characteristics).
Noise measurements are key to assuring that added noise is minimal. The need for highly repeatable, accurate and meaningful measurements of noise without the complexity of manual measurements and calculations has led to the development of noise figure measurement instruments with simple user interfaces.