# WVD Spectrogram (G Dataflow)

Version:

Computes the energy distribution of the input signal in the joint time-frequency domain using the Wigner-Ville distribution (WVD) algorithm.

## reset

A Boolean that specifies whether to reset the internal state of the node.

 True Resets the internal state of the node. False Does not reset the internal state of the node.

This input is available only if you wire a double-precision, floating-point number to x.

Default: False

## x

The input time-domain signal.

This input accepts the following data types:

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

## time steps

Time intervals, in units of samples, of the Wigner-Ville Distribution (WVD).

Performance Considerations

Increasing time steps decreases the computation time and reduces memory requirements but also reduces time-domain resolution. Decreasing time steps improves time-domain resolution but increases the computation time and memory requirements.

Default: 1

## sample length

Length of each set of data. The node performs computation for each set of data.

sample length must be greater than zero.

This input is available only if you wire a double-precision, floating-point number to x.

Default: 100

## 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

## WVD spectrogram

The energy distribution of the input signal in the joint time-frequency domain.

## 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.

## Algorithm for Calculating the Spectrogram Using the Wigner-Ville Distribution (WVD)

For a discrete signal X, with an analytic associate of Z, the following equation defines the Wigner-Ville Distribution (WVD) of the analytic associate, ${\text{WVD}}_{Z}\left(n,f\right)$:

${\text{WVD}}_{Z}\left(n,f\right)=2\underset{k=-\infty }{\overset{\infty }{\sum }}Z\left(n+k\right)Z*\left(n-k\right){e}^{-j4\pi fk}$

where

• n is the index in the time domain
• f is the index in the frequency domain
• Z is the analytic associate defined as $\text{X}+i*H\left[\text{X}\right]$, where $H\left[\text{X}\right]$ is the Hilbert Transform of X

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

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