Article
Article
Signal-to-noise ratio
Article By:
Helgert, Hermann J. Department of Electrical and Computer Engineering, George Washington University, Washington, DC.
Last reviewed:January 2020
DOI:https://doi.org/10.1036/1097-8542.622200
The quantity that measures the relationship between the strength of an information-carrying signal in an electrical communications system and the random fluctuations in amplitude, phase, and frequency superimposed on that signal and collectively referred to as noise. For analog signals, the ratio, denoted S/N, is usually stated in terms of the relative amounts of electrical power contained in the signal and the noise. For digital signals, the ratio is defined as the amount of energy in the signal per bit of information carried by the signal, relative to the amount of noise power per hertz of signal bandwidth (the noise power spectral density), and is denoted Eb/N0. Since both signal and noise fluctuate randomly with time, S/N and Eb/N0 are specified in terms of statistical or time averages of these quantities.
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