Noise floor
Encyclopedia
In signal theory, the noise floor is the measure of the signal created from the sum of all the noise
sources and unwanted signals within a measurement system, where the noise is defined as any signal other than the one being monitored.
In radio communication and electronics, this may include thermal noise, blackbody, cosmic noise
as well as Atmospheric noise
from distant thunderstorms and similar and any other unwanted man made signals, sometimes referred to as incidental noise . If the dominant noise is generated within the measuring equipment (for example by a receiver with a poor noise figure
) then this is an example of an instrumentation noise floor, as opposed to a physical noise floor . These terms are not always clearly defined, and are sometimes confused. .
Avoiding interference between electrical systems is the distinct subject of electromagnetic compatability EMC
.
In a measurement system such as a seismograph, the physical noise floor may be set by the incidental noise, and include nearby foot traffic or a nearby road. The noise floor limits the smallest measurement that can be taken with certainty since any measured amplitude can on average be no less than the noise floor.
A common way to lower the noise floor in electronics systems is to cool the system to reduce thermal noise, when this is the major noise source. In special circumstances, the noise floor can also be artificially lowered with digital signal processing
techniques.
Signals that are below the noise floor can be detected by using different techniques of spread spectrum
communications, that effectively reduce the bandwidth of the signal.
Noise
In common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
sources and unwanted signals within a measurement system, where the noise is defined as any signal other than the one being monitored.
In radio communication and electronics, this may include thermal noise, blackbody, cosmic noise
Cosmic noise
Cosmic noise and galactic radio noise is random noise that originates outside the Earth's atmosphere. It can be detected and heard on radio receivers.- Elaboration :Cosmic noise characteristics are similar to those of thermal noise...
as well as Atmospheric noise
Atmospheric noise
Atmospheric noise is radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorms. On a worldwide scale, eight million lightning discharges per day — about 100 lightning flashes per second.-History:...
from distant thunderstorms and similar and any other unwanted man made signals, sometimes referred to as incidental noise . If the dominant noise is generated within the measuring equipment (for example by a receiver with a poor noise figure
Noise figure
Noise figure is a measure of degradation of the signal-to-noise ratio , caused by components in a radio frequency signal chain. The noise figure is defined as the ratio of the output noise power of a device to the portion thereof attributable to thermal noise in the input termination at standard...
) then this is an example of an instrumentation noise floor, as opposed to a physical noise floor . These terms are not always clearly defined, and are sometimes confused. .
Avoiding interference between electrical systems is the distinct subject of electromagnetic compatability EMC
EMC
EMC may refer to:In organizations:* EMC Corporation, an information management company* IEEE Electromagnetic Compatibility Society, a worldwide professional engineering society* Eastern Media Centre, a television channel in the UK...
.
In a measurement system such as a seismograph, the physical noise floor may be set by the incidental noise, and include nearby foot traffic or a nearby road. The noise floor limits the smallest measurement that can be taken with certainty since any measured amplitude can on average be no less than the noise floor.
A common way to lower the noise floor in electronics systems is to cool the system to reduce thermal noise, when this is the major noise source. In special circumstances, the noise floor can also be artificially lowered with digital signal processing
Digital signal processing
Digital signal processing is concerned with the representation of discrete time signals by a sequence of numbers or symbols and the processing of these signals. Digital signal processing and analog signal processing are subfields of signal processing...
techniques.
Signals that are below the noise floor can be detected by using different techniques of spread spectrum
Spread spectrum
Spread-spectrum techniques are methods by which a signal generated in a particular bandwidth is deliberately spread in the frequency domain, resulting in a signal with a wider bandwidth...
communications, that effectively reduce the bandwidth of the signal.
See also
- NoiseNoiseIn common use, the word noise means any unwanted sound. In both analog and digital electronics, noise is random unwanted perturbation to a wanted signal; it is called noise as a generalisation of the acoustic noise heard when listening to a weak radio transmission with significant electrical noise...
- thermal noise
- blackbody
- cosmic noiseCosmic noiseCosmic noise and galactic radio noise is random noise that originates outside the Earth's atmosphere. It can be detected and heard on radio receivers.- Elaboration :Cosmic noise characteristics are similar to those of thermal noise...
- Atmospheric noiseAtmospheric noiseAtmospheric noise is radio noise caused by natural atmospheric processes, primarily lightning discharges in thunderstorms. On a worldwide scale, eight million lightning discharges per day — about 100 lightning flashes per second.-History:...
- Noise (electronic)
- Noise figure meterNoise figure meterA noise figure meter is an instrument for measuring the noise figure of an amplifier, mixer, or similar device. An example instrument is the 1983-era Agilent 8970A.- Measurement methods :...
- Noise level
- Thermal noise
- Signal-to-noise ratioSignal-to-noise ratioSignal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
- Y-factorY-factorThe Y-factor method is a widely used technique for measuring the gain and noise temperature of an amplifier. It is based on the Johnson-Nyquist noise of a resistor at two different, known temperatures....