Nyquist frequency - definition
Nyquist frequency - definition
The Nyquist Frequency is a concept in the theory of signal processing, which defines the maximum frequency of the component of an analogue signal that can be correctly reproduced with digital sampling. It is equal to half the sampling frequency, which is the number of samples taken from the signal per unit time. According to the Nyquist-Shannon theorem, in order to avoid distortion when reconstructing a signal from samples, it is necessary to sample it at a frequency at least twice as high as the highest frequency present in that signal.
This concept plays a fundamental role in analogue-to-digital conversion (ADC) systems, data transmission and digital audio and video processing. In practice, the use of a sampling frequency higher than that required by the Nyquist frequency provides a margin of safety and reduces the risk of aliasing - a phenomenon involving the overlapping of signal spectra, which leads to the loss of information and the generation of spurious components in the reconstructed signal.
The Nyquist frequency is not the same as the maximum frequency of the signal analysed, but is a limit value that this signal should not exceed in order to comply with the accepted sampling frequency. In digital systems, additional anti-aliasing filters are used to attenuate signal components above this limit even before sampling.
This concept also has applications in discrete systems theory, spectral analysis and the design of digital filters. Knowledge of the Nyquist frequency is crucial in the design of measurement systems, data acquisition and information processing, where maintaining the integrity of the original signal is important for the quality of the final result.
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