Difference Between Noise Figure And Noise Floor

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Difference between noise figure and noise floor.

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. If we need the signal to be 10 times more powerful than the noise floor the required snr would be 10 db. 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. Noise figure is just log scaled value of noise factor as shown below.

Noise is always present and received on a radio even when no wanted signals are present. Noise level is expressed by the amplifier noise figure. It defines how much noise is added by any amplifier while amplifying the signal. To calculate the actual minimum detectable signal is simply a case of adding the required snr in db to the noise floor.

This page on noise factor versus noise figure describes difference between noise factor and noise figure. This is all about the noise figure but if you want to play more with math. The noise figure for a circuit is the. Noise floor can be derived from the gain g input noise ni and the internally generated noise na as shown below.

Thus noise figure is independent of the input signal level. So this may well be where these two become even more of an issue. So for the example above this would mean that the minimum detectable signal is. The noise power from a simple load is equal to ktb where k is boltzmann s constant t is.

Noise factor versus 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. 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.