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Pattern Generator (Sinc) (G Dataflow)

Last Modified: January 12, 2018

Generates a signal containing a sinc pattern.

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amplitude

Amplitude of the pattern.

Default: 1

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delay

Shifts the peak value within the output pattern as the node generates the pattern. The peak value of the output pattern occurs at the index value i = delay/(dt).

Default: 0

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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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dt

Sampling interval. This floating-point number is inversely proportional to the width of the main sinc lobe. That is, the smaller the sampling interval, the wider the main lobe; the larger the sampling interval, the smaller the main lobe. When this input is 1 and delay is an integer value, this node sets the output pattern to zero except at the point where i = delay. At this point, the value is equal to amplitude. The recommended range of values for the sampling interval is between 0 and 1. This input must be greater than 0. If this input is less than or equal to zero, this node sets the output pattern to an empty array and returns an error.

Default: 0.1

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samples

Number of samples in the pattern.

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

Default: 128

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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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sinc pattern

Output sinc pattern. The largest output pattern this node can generate depends on the amount of memory in your system and is theoretically limited to 2,147,483,647 (231 - 1) elements.

This output can return a waveform or an array of double-precision, floating-point numbers.

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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.

Algorithm for Generating the Sinc Pattern

If the sequency Y represents sinc pattern, this node generates the pattern according to the following equation:

y i = a sinc ( i Δ t d )

for i = 0, 1, 2, ..., n - 1

where

  • sinc ( x ) = sin ( π x ) π x
  • a is amplitude
  • Δ t is the sampling interval dt
  • d is delay
  • n is samples

The main lobe of the sinc function, sinc(x), is the part of the sinc curve bounded by the region 1 x 1 .

When |x| = 1, sinc(x) = 0.0 and the peak value of the sinc function occurs when x = 0. Using L'Hopital's Rule, you can show that sinc(0) = 1 and that this is also its peak value. Thus, the main lobe is the region of the sinc curve encompassed by the first set of zeros to the left and the right of the sinc value.

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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