Nyquistfrekvenssi

Nyquistfrekvenssi, often referred to as the Nyquist frequency in English, is a fundamental concept in digital signal processing. It is defined as half the sampling rate of a discrete-time system. For example, if a signal is sampled at a rate of 1000 samples per second, its Nyquist frequency is 500 Hz.

The significance of the Nyquist frequency lies in the Nyquist-Shannon sampling theorem. This theorem states that a continuous-time signal can be perfectly reconstructed from its samples if and only if its frequency content is limited to below the Nyquist frequency. In simpler terms, to accurately capture all the information in a signal, the sampling rate must be at least twice the highest frequency component present in that signal.

If a signal contains frequencies higher than the Nyquist frequency, these higher frequencies can masquerade as lower frequencies in the sampled data. This phenomenon is known as aliasing and leads to distortion of the reconstructed signal. Therefore, to avoid aliasing, signals are typically passed through a low-pass filter (an anti-aliasing filter) before sampling to remove any frequencies above the desired Nyquist frequency. The Nyquist frequency is thus a critical parameter in determining the appropriate sampling rate for a given application, ensuring the fidelity of digital representations of analog signals.