Noise floor

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Measurement from a spectrum analyzer showing a noise-like measurement from an unspecified component. Spectrum analyzer, display, noise floor.jpg
Measurement from a spectrum analyzer showing a noise-like measurement from an unspecified component.

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 noise is defined as any signal other than the one being monitored.

In radio communication and electronics, this may include thermal noise, black body, 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. [1]

Avoiding interference between electrical systems is the distinct subject of electromagnetic compatibility (EMC).

In a measurement system such as a seismograph, the physical noise floor may be set by the incidental noise, and may 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, where signal of a particular information bandwidth is deliberately spread in the frequency domain resulting in a signal with a wider occupied bandwidth.

Every additional 6.02 dB of noise floor corresponds to a 1-bit reduction of the effective number of bits of an analog-to-digital converter or digital-to-analog converter.

See also

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<span class="mw-page-title-main">Noise (electronics)</span> Random fluctuation in an electrical signal

In electronics, noise is an unwanted disturbance in an electrical signal.

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Spurious-free dynamic range (SFDR) is the strength ratio of the fundamental signal to the strongest spurious signal in the output. It is also defined as a measure used to specify analog-to-digital and digital-to-analog converters and radio receivers.

In computing, bandwidth is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth, data bandwidth, or digital bandwidth.

In signal processing, noise is a general term for unwanted modifications that a signal may suffer during capture, storage, transmission, processing, or conversion.

References

  1. "Notes on the RSGB Observations of the HF Ambient Noise Floor" (PDF). Radio Society of Great Britain. Retrieved 2014-02-03.