Nyquist sampling theorem

Video tutorial
The Nyquist sampling theorem is a fundamental result in the field of information theory, in particular telecommunications and signal processing. In layman's terms the theory states that a bandlimited analog signal that has been sampled can be perfectly reconstructed from an infinite sequence of samples if the sampling rate exceeds 2B samples per second, where B is the highest frequency in the original signal.

This theorem is also known as:


 * Nyquist-Shannon sampling theorem
 * Nyquist-Shannon-Kotelnikov
 * Whittaker-Shannon-Kotelnikov
 * Whittaker-Nyquist-Kotelnikov-Shannon
 * Cardinal Theorem of Interpolation Theory

If the sampling rate is insufficient (in other words, less than double the highest frequency in the original signal), a phenomenon known as "Nyquist foldover" is observed. The phenomenon causes frequencies greater than half the sampling rate to be reconstructed as frequencies an equivalent distance below the sampling rate; for instance, a signal at 100 Hz that is sampled at 180Hz will be reconstructed as a signal at ((180/2)-10) = 80 Hz. This phenomenon is also observed in other media, such as with the capture of car wheels or helicopter rotors on film.

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