The Nyquist-Shannon sampling theorem, often simply referred to as the Nyquist theorem or Nyquist sampling theorem, is a fundamental principle in digital signal processing and communication theory. It was developed by Harry Nyquist and later popularized by Claude Shannon. The theorem establishes a relationship between the sampling rate and the original analog signal, ensuring that the sampled signal can be accurately reconstructed without loss of information.
The Nyquist theorem states that in order to accurately reconstruct a continuous analog signal from its samples, the sampling frequency (rate) must be at least twice the highest frequency present in the original analog signal. In other words:
Sampling Rate ≥ 2 × Maximum Frequency of the Analog Signal
This means that to avoid aliasing and accurately capture the original signal's information, you need to sample the signal at a rate that allows at least two samples to be taken during each full cycle of the highest frequency component in the analog signal. When the sampling rate is insufficient, aliasing occurs, leading to distorted and erroneous representations of the original signal.
In practical terms, when dealing with digital audio signals or any continuous-time signal that needs to be processed digitally, adhering to the Nyquist theorem becomes crucial. For example, when digitizing an audio signal, the sampling rate must be at least twice the highest frequency present in the audio (the audible frequency range typically goes up to around 20 kHz).
The Nyquist theorem has far-reaching implications in various fields like digital signal processing, telecommunications, data acquisition, and more. Adhering to the Nyquist theorem is essential to ensure that the digital representation of analog signals accurately preserves their information and characteristics, allowing for faithful reconstruction and subsequent processing.