# Noise Generator (Periodic Random) (G Dataflow)

Version:

Generates a waveform containing periodic random noise (PRN).

You can use periodic random noise to compute the frequency response of a linear system in one time record instead of averaging the frequency response over several time records, as you must for nonperiodic random noise sources.

## reset

A Boolean that controls the reseeding of the noise sample generator after the first execution of the node. By default, this node maintains the initial internal seed state.

 True Accepts a new seed and begins producing noise samples based on the seed. If the given seed is less than or equal to 0, the node ignores a reset value of True and resumes producing noise samples as a continuation of the previous sequence. False Resumes producing noise samples as a continuation of the previous noise sequence. The node ignores new seed inputs while reset is False.

Default: False

## spectral amplitude

Magnitude of the frequency domain components of the output signal.

Default: 1

## seed

A number that initializes the noise generator.

If reset is unwired, this node maintains the internal seed state.

 seed is greater than 0 Generates noise samples based on the given seed value. For multiple calls to the node, the node accepts or rejects new seed inputs based on the given reset value. seed is less than or equal to 0 Generates a random seed value and produces noise samples based on that seed value. For multiple calls to the node, if seed remains less than or equal to 0, the node ignores the reset input and produces noise samples as a continuation of the initial noise sequence.

Default: -1

## 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

## sample rate

Sample rate in samples per second.

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

Default: 1000

## samples

Number of samples in the signal.

Default: 1000

## 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.

## periodic random noise

The periodic random noise pattern.

This output can return the following data types:

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

Understanding the Output Array

The output periodic random noise contains all frequencies that can be represented with an integral number of cycles in the requested number of samples. Each frequency-domain component has a magnitude of spectral amplitude and random phase.

Another way of thinking of periodic random noise is that it is a summation of sinusoidal signals with the same amplitudes but with random phases. The unit of spectral amplitude is the same as periodic random noise and is a linear measure of amplitude.

The following values bound the periodic random noise:

$\mathrm{spectralamplitude}*\left(\frac{\mathrm{samples}}{2}-1\right)\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}\text{\hspace{0.17em}}$

if samples is even

$\mathrm{spectralamplitude}*\frac{\mathrm{samples}-1}{2}$

if samples is odd

## 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.

## Windowing the Periodic Random Noise

Periodic random noise contains only integral-cycle sinusoids, which means the noise is self-windowing and does not contains spectral leakage. As a result, you do not need to window periodic random noise before performing spectral analysis.

Where This Node Can Run:

Desktop OS: Windows

FPGA: This product does not support FPGA devices