Glossary Definition for Aliasing

Definition

In A/D conversion, the Nyquist principle states that the sampling rate must be at least twice the maximum bandwidth of the analog signal. If the sampling rate is insufficient, then higher-frequency components are "undersampled" and appear shifted to lower-frequencies. These frequency-shifted components are called aliases.

The frequencies that shift are sometimes called "folded" frequencies because a spectral plot looks like it was folded to superimpose the higher frequency components over the sub-Nyquist portion of the band.

Also see:

• Application Note/Tutorial: Filter Basics: Anti-Aliasing
• The Basics of Anti-Aliasing: Using Switched-Capacitor Filters
• Mathematical Basics of Band-Limited Sampling and Aliasing
• Folded-Frequency Calculator

Synonyms

• alias
• folded-frequency

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