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Anti-aliasing filter

A filter applied before sampling to force a real signal's spectrum closer to band-limited.

An anti-aliasing filter removes a signal's content above some cutoff frequency before it is sampled, forcing the band-limited hypothesis to hold as closely as real hardware allows and so avoiding the aliasing that sampling an unfiltered signal would otherwise cause.

Examples

  • An audio recording chain filters out everything above roughly 20-22 kHz before sampling at 44.1 kHz.

See also

Band-limited (to $B$ Hz) Aliasing
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