Difference Between Noise Figure And Noise Floor

Noise level is expressed by the amplifier noise figure.

Difference between noise figure and noise floor.

Noise figure is just log scaled value of noise factor as shown below. The noise figure is the difference in decibels db between the noise output of the actual receiver to the noise output of an ideal receiver with the same overall gain and bandwidth when the receivers are connected to matched sources at the standard noise temperature t 0 usually 290 k. The noise power from a simple load is equal to ktb where k is boltzmann s constant t is. This page on noise factor versus noise figure describes difference between noise factor and noise figure.

The level of the noise floor determines the lowest strength signals that can be received and therefore the noise floor level is an important characteristic of any radio. The noise figure for a circuit is the. Noise factor versus noise figure. Then there is weighted noise figure measured when a frequency is applied to the noise floor.

Noise floor can be derived from the gain g input noise ni and the internally generated noise na as shown below. Note that if the input signal level were 5 db lower 35 db above the noise floor it would also be 5 db lower at the out put 25 db above the noise floor and the noise figure would still be 10 db. It defines how much noise is added by any amplifier while amplifying the signal. Thus noise figure is independent of the input signal level.

The relative noise contribution of the five stages shows that after the lna not much else is added to the noise factor. So this may well be where these two become even more of an issue. Mds 92 5 10 82 5. So for the example above this would mean that the minimum detectable signal is.

By the way don t spend any time thinking about gain and noise figure beyond one or two decimal digits in practice you ll never be able to measure the difference between 3 812 and 3 8 db. To calculate the actual minimum detectable signal is simply a case of adding the required snr in db to the noise floor. This is all about the noise figure but if you want to play more with math.