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Nyquist's criterion


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The statement that when a continuous-time band-limited channel is to be sampled, the sampling process may or may not cause information to be lost according to whether the sampling rate, ν, is less than, greater than, or equal to twice the bandwidth, W.

If ν = 2W, sampling is said to occur at the Nyquist rate.

if ν < 2W, sub-Nyquist sampling is said to take place, and some information will be lost; this may be quite acceptable in certain cases.

If ν > 2W, super-Nyquist sampling occurs; it cannot cause any more information to be extracted than sampling at the Nyquist rate.

Super-Nyquist sampling (at somewhat over the Nyquist rate) is, however, commonly employed to allow a margin of safety since there may be some doubt about the actual value of the bandwidth. There is no harm in it, if it is convenient, but the samples taken at a super-Nyquist rate will not be independent of one another.

See also discrete and continuous systems.

Subjects: Computing.


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