The '''Nyquist–Shannon sampling theorem''' is an essential principle offor [[digital signal processing]] linking the [[frequency range]] of a signal and the [[sample rate]] required to avoid a type of distortion called [[aliasing]]. The theorem states that the sample rate must be at least twice the [[bandwidth]] of the signal to avoid aliasing distortion. In practice, it is used to select [[band-limiting]] filters to keep aliasing distortion below an acceptable amount when an analog signal is sampled or when sample rates are changed within a digital signal processing function.
[[File:Bandlimited.svg|thumb|250px|Example of magnitude of the Fourier transform of a bandlimited function]]
