MT Format Constellation VI

LabView Digital Modulation

MT Format Constellation VI

Prepares a signal for presentation on a graph showing the detected symbol locations and the transitions between those symbols. The VI specifies a complex-valued waveform and displays a constellation plot of the waveform contents.

Details

MT Format Constellation

waveform specifies the recovered modulated data for plotting as a constellation.

	t0 specifies the trigger (start) time of the Y array. The default is 0.0.
	dt specifies the time interval between data points in the Y array. The default is 1.0.
	Y specifies the complex-valued signal-only baseband modulated waveform. The real and imaginary parts of this complex data array correspond to the in-phase (I) and quadrature-phase (Q) data, respectively.

samples per symbol specifies the number of samples per symbol in the recovered waveform. The default is 0.

autoscale specifies whether to apply autoscaling to the graph referenced in the constellation reference control. When this control is set to TRUE, the vertical and horizontal axes of the plot are scaled symmetrically about zero, with enough room to accommodate the largest signal value. The default is FALSE (not autoscaling).

constellation reference specifies a reference to the graph wired to the constellation graph parameter. This connection is prewired when you drop the VI from the front panel Controls palette.

error in (no error) can accept error information wired from previously called VIs. Use this information to decide if any functionality should be bypassed in the event of errors from other VIs. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code identifies the error or warning code. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error in control and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

constellation graph returns a two-element array of XY data. The first element is the constellation; the second element is the oversampled data. Wire this parameter directly to an XY graph.

Note If you originally placed this VI onto the front panel from the Controls palette as a new waveform graph, the constellation graph parameter is prewired to the graph.

	constellation returns an array of doubles representing the constellation plot.
	oversampled data returns an array of doubles representing the oversampled data.

error out passes error or warning information out of a VI to be used by other VIs. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

	status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	code is the error or warning code. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.
	source describes the origin of the error or warning. Right-click the front panel error out indicator and select Explain Error or Explain Warning from the shortcut menu for more information about the error.

Details

This VI assumes that the input waveform is a digitally modulated complex baseband signal containing samples that fall on symbol boundaries with a sample rate that is an integer multiple of the samples per symbol value.

Although this VI performs no demodulation or frequency correction, you can use this VI to examine the output of many of the digital demodulation VIs. In cases where the demodulator can recover symbol timing, the output complex waveform parameter of the digital demodulation VIs contains a frequency-corrected signal appropriate for plotting with this VI.

This VI works in conjunction with a standard LabVIEW graph indicator and is available both from the front panel Controls palette (Controls»Modulation»Digital) and from the block diagram Functions palette (Functions»Modulation»Digital»Utilities).

When selected from the front panel Controls palette, this VI is automatically prewired to the appropriate graph. When this VI is placed from the Functions palette, no connections are automatically wired and you must manually connect the graph indicator on the block diagram.

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