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Noise Generator (Inverse f) (G Dataflow)

Last Modified: January 12, 2018

Generates a continuous noise waveform with a power spectral density that is inversely proportional to frequency over a specified frequency range.

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reference frequency

Frequency in Hz at which the spectral density of the ideal inverse-f noise waveform is equal to the noise density you specified.

The actual inverse-f noise waveform source is designed to approximate the ideal inverse-f noise waveform over the frequency range defined in filter specifications. Therefore, the actual spectral density of the inverse-f noise waveform at reference freq is near noise density if reference freq is within the design frequency range specified in filter specifications.

Default: 1

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reset

A Boolean that controls the reseeding of the noise sample generator after the first call of the node.

True Accepts a new seed and begins producing noise samples based on seed.
False Maintains the initial internal seed state and resumes producing noise samples as a continuation of the previous noise sequence.

Default: False

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noise density

Spectral density (V/root Hz) of the ideal inverse-f noise waveform at the reference frequency.

The actual inverse-f noise waveform approximates the ideal inverse-f noise over the frequency range defined by filter specifications. Therefore, the actual spectral density of the inverse-f noise waveform at reference freq is near noise density only if reference freq is within the design frequency range specified in filter specifications.

Default: 0.1

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exponent

Exponent of the desired inverse-f spectral shape. This node designs a digital filter with the desired magnitude-squared response of 1/frequencyexponent.

Default: 1

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filter specifications

Operating frequency range and the filter order of the filter.

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lower cutoff freq

Lower frequency edge of the operating frequency range of the filter.

Default: 0.1

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higher cutoff freq

Higher frequency edge of the operating frequency range of the filter.

Default: 100

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order

Number of first order stages of the inverse-f filter.

Increasing order improves the inverse-f spectral shape but requires more computation time during the filter operation.

Default: 5

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seed

Number that this node uses to initialize the noise generator.

This node initializes the noise generator using seed if reset is True or if this is the first call of the node.

seed is greater than 0 Generates noise samples based on the seed value.
seed is less than or equal to 0 For the first call, this node generates a random seed value and produces noise samples based on that seed value. For subsequent calls to the node, if seed remains less than or equal to 0, the node maintains the initial internal seed state and produces noise samples as a continuation of the initial noise sequence.

Default: -1

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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

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sample rate

Sampling rate in samples per second.

Default: 1000

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samples

Number of samples in the signal.

samples must be greater than 0. Otherwise, this node returns an error.

This input is available when you configure this node to return a waveform or an array of double-precision, floating-point numbers.

Default: 1000

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t0

Timestamp of the output signal. If this input is unwired, this node uses the current time as the timestamp of the output signal.

This input is available only if you configure this node to return a waveform.

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inverse f noise

Generated inverse-f noise waveform.

This output can return the following data types:

  • Waveform
  • Double-precision, floating-point number
  • 1D array of double-precision, floating-point numbers
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magnitude error

Magnitude of the deviation of the actual inverse-f filter, in decibels, when measured against the ideal inverse-f filter.

The ideal filter has a magnitude-squared response proportional to 1/f exponent over the frequency range specified by low cutoff frequency, high cutoff frequency, and order.

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frequency (Hz)

Frequencies of the magnitude error in Hz.

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magnitude (dB)

Magnitudes of the magnitude error in dB.

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expected rms

Expected RMS level of the generated noise waveform.

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filter information

Magnitude and phase of the frequency response of the designed inverse-f filter.

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magnitude (dB)

Magnitude of the frequency response of the designed inverse-f filter in dB.

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frequency (Hz)

Frequencies of the frequency response of the designed inverse-f filter in Hz.

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magnitude (dB)

Magnitudes of the frequency response of the designed inverse-f filter in dB.

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phase (deg)

Phase of the frequency response of the designed inverse-f filter in degrees.

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frequency (Hz)

Frequencies of the frequency response of the designed inverse-f filter in Hz.

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phase (deg)

Phases of the frequency response of the designed inverse-f filter in degrees.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application


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