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Nyquist Frequency

  1. G. J. Janacek

Published Online: 15 JUL 2005

DOI: 10.1002/0470011815.b2a12054

Encyclopedia of Biostatistics

Encyclopedia of Biostatistics

How to Cite

Janacek, G. J. 2005. Nyquist Frequency. Encyclopedia of Biostatistics. 6.

Author Information

  1. University of East Anglia, Norwich, UK

Publication History

  1. Published Online: 15 JUL 2005

Abstract

If we sample a signal observed over time at intervals, perhaps by digitizing an analog signal, then we naturally expect some loss of information. If the observed signal has cyclic components, then the sampling may induce some distortion in the effects we see in the sampled results.

There are some cyclic effects that are not observable, at least directly, and these are ones with high frequencies (or short periods). The frequency beyond which cyclic effects are unobservable is called the Nyquist or folding frequency. This frequency is related to the sampling rate Δt and is in fact 1/2Δt cycles per unit time.

Keywords:

  • folding frequency;
  • sampling;
  • digitizing;
  • discrete;
  • analogue to digital