# Nyquist frequency

NyquistN/2 different frequenciesNyquist componentNyquist criterionNyquist imagesnyquist 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 quantity ½ cycles/sample × f s samples/sec = f s /2 cycles/sec (hertz) is known as the Nyquist frequency of the sampler.

### Aliasing

aliasedaliastemporal 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 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 limitNyquist sampling rateNyquist
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.
1) as a lower bound for the sample rate for alias-free signal sampling (not to be confused with the Nyquist frequency, which is half the sampling rate of a discrete-time system) and

### 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.
Nyquist frequency: half the sample rate of a system; signal frequencies below this value are unambiguously represented.

### Nyquist–Shannon sampling theorem

sampling theoremsampling theoryNyquist
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.

### 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

pitch perceptionaudible rangerange 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 soundanalog versus digital sound
The bandwidth of the digital system is determined, according to the Nyquist frequency, by the sample rate used.

### High-resolution audio

HDhigh-resolutionHD Audio
It usually means 96 kHz (or even much higher), sometimes informally written as "96k", meaning a Nyquist frequency of 48 kHz.

### 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.

### Magnetometer

digital compassDigitalmagnetometers
Bandwidth or bandpass characterizes how well a magnetometer tracks rapid changes in magnetic field. For magnetometers with no onboard signal processing, bandwidth is determined by the Nyquist limit set by sample rate. Modern magnetometers may perform smoothing or averaging over sequential samples. achieving a lower noise in exchange for lower bandwidth.

### Critical frequency

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

### 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.

### 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.

### Compact Disc Digital Audio

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

### Eagle eye

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

### Digital signal processing

DSPsignal processingdigital signal processing (DSP)
In practice, the sampling frequency is often significantly higher than twice the Nyquist frequency.

### 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

filteringmultivariate interpolation kernelsreconstruction
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.