Nyquist frequency

Nyquist limitNyquistN/2 different frequenciesNyquist componentNyquist criterionNyquist imagesNyquist sampling limitNyquist velocity
The Nyquist frequency, named after electronic engineer Harry Nyquist, is half of the sampling rate of a discrete signal processing system.wikipedia
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Sampling (signal processing)

sampling ratesamplingsample rate
The Nyquist frequency, named after electronic engineer Harry Nyquist, is half of the sampling rate of a discrete signal processing system.
The original signal is retrievable from a sequence of samples, up to the Nyquist limit, by passing the sequence of samples through a type of low pass filter called a reconstruction filter.

Aliasing

aliasaliasedtemporal aliasing
It is sometimes known as the folding frequency of a sampling system.
If a piece of music is sampled at 32000 samples per second (Hz), any frequency components at or above 16000 Hz (the Nyquist frequency for this sampling rate) will cause aliasing when the music is reproduced by a digital-to-analog converter (DAC).

Nyquist rate

Nyquist sampling rateNyquist limitNyquist
The Nyquist frequency should not be confused with the Nyquist rate, the latter is the minimum sampling rate that satisfies the Nyquist sampling criterion for a given signal or family of signals.

Nyquist–Shannon sampling theorem

sampling theoremNyquist-Shannon sampling theoremNyquist theorem
The Nyquist frequency should not be confused with the Nyquist rate, the latter is the minimum sampling rate that satisfies the Nyquist sampling criterion for a given signal or family of signals.
The threshold f s /2 is called the Nyquist frequency and is an attribute of the sampling equipment.

Harry Nyquist

NyquistNyquist, Harry
The Nyquist frequency, named after electronic engineer Harry Nyquist, is half of the sampling rate of a discrete signal processing system.

Anti-aliasing filter

anti-aliasinganti-aliasing (AA) filteroptical low-pass filter
Then one inserts an anti-aliasing filter ahead of the sampler.
Since the theorem states that unambiguous reconstruction of the signal from its samples is possible when the power of frequencies above the Nyquist frequency is zero, a real anti-aliasing filter trades off between bandwidth and aliasing.

Discrete time and continuous time

discrete timediscrete-timecontinuous-time
The Nyquist frequency, named after electronic engineer Harry Nyquist, is half of the sampling rate of a discrete signal processing system.

Cycle per second

kilocyclecycles per secondkilocycles
When the function domain is time, sample rates are usually expressed in samples per second, and the unit of Nyquist frequency is cycles per second (hertz).

Hertz

MHzkHzHz
When the function domain is time, sample rates are usually expressed in samples per second, and the unit of Nyquist frequency is cycles per second (hertz).

Compact disc

CDCDsCD single
For example, audio CDs have a sampling rate of 44100 samples/sec.

44,100 Hz

44.1 kHz44.1kHz44,100 samples per second
For example, audio CDs have a sampling rate of 44100 samples/sec.

Hearing range

audible rangepitch perceptionrange of human hearing
The anti-aliasing filter must adequately suppress any higher frequencies but negligibly affect the frequencies within the human hearing range.

Comparison of analog and digital recording

analogAnalog sound vs. digital soundAnalog recording vs. digital recording
The bandwidth of the digital system is determined, according to the Nyquist frequency, by the sample rate used.

High-resolution audio

high-resolutionHDHD Audio
It commonly refers to 96 kHz or 192 kHz sample rates, producing a Nyquist frequency of 48 kHz or more.

Chirp spectrum

The simplest way to derive the spectrum of a chirp, now that computers are widely available, is to sample the time-domain waveform at a frequency well above the Nyquist limit and call up an FFT algorithm to obtain the desired result.

Bitcrusher

bit crusherbitcrushingbit-reduced
Specifically, the frequency of sampling (a.k.a. the sample rate) must be at least twice the maximum frequency component in the signal; this maximum signal frequency of one half the sampling frequency is called the Nyquist limit.

Critical frequency

Critical Frequency (foF2)
In signal processing the critical frequency it is also another name for the Nyquist frequency.

Compact Disc Digital Audio

Audio CDCDCD-DA
An audio CD can represent frequencies up to 22.05 kHz, the Nyquist frequency of the 44.1 kHz sample rate.

Impulse invariance

The frequency response of the discrete-time system will be a sum of shifted copies of the frequency response of the continuous-time system; if the continuous-time system is approximately band-limited to a frequency less than the Nyquist frequency of the sampling, then the frequency response of the discrete-time system will be approximately equal to it for frequencies below the Nyquist frequency.

Analog-to-digital converter

ADCanalog to digital converteranalog-to-digital conversion
Quantization error is distributed from DC to the Nyquist frequency, consequently if part of the ADC's bandwidth is not used, as is the case with oversampling, some of the quantization error will occur out-of-band, effectively improving the SQNR for the bandwidth in use.

Eagle eye

An eagle's retina allows for a higher Nyquist limit.

Nicolet 1080

The Analog to Digital Converter (ADC) had a sample rate of 100 kHz, allowing the measure of 50 kHz signals (see Nyquist frequency).

Reconstruction filter

filteringFiltering by reconstructionmultivariate interpolation kernels
Ideally, both filters should be brickwall filters, constant phase delay in the pass-band with constant flat frequency response, and zero response from the Nyquist frequency.

Digital audio

digital musicdigitalaudio
Analog signals that have not already been bandlimited must be passed through an anti-aliasing filter before conversion, to prevent the aliasing distortion that is caused by audio signals with frequencies higher than the Nyquist frequency (half the sampling rate).