MT Decimate Oversampled Waveform VI

LabView Digital Modulation

MT Decimate Oversampled Waveform VI

Decimates the input complex waveform and returns the decimated output complex waveform. Use this VI to decimate the matched filtered waveform at the output of the MT Matched Filter VI to recover the symbols corresponding to the ideal symbol timing location.

Details

MT Decimate Oversampled Waveform

input complex waveform specifies the modulated complex baseband waveform data.

	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.

decimation factor specifies the extent to which the input complex waveform is decimated. This parameter is ignored on subsequent calls when reset? is set to FALSE.

Tip If you are recovering the ideal symbol timing instant, ensure that this input value matches the samples per symbol parameter to the MT Matched Filter VI.

offset specifies the starting index of the Y array within the input complex waveform cluster from which decimation is performed. This parameter is ignored on subsequent calls when reset? is set to FALSE. Samples prior to the specified offset are discarded. Use this parameter to specify the first sample containing an ideal symbol timing instant. The default is 0 (no samples discarded).

reset? specifies whether stored state information is cleared at subsequent calls to this VI. When reset? is set to TRUE, decimation begins at the starting point specified by offset. When reset? is set to FALSE, the specified offset and decimation factor values are used on first call only, and computed on subsequent calls to ensure continuability from one iteration to the next. The default is TRUE.

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.

output complex waveform returns the decimated I/Q baseband waveform sampled at a rate 1/(decimation factor × dt) seconds/sample.

	t0 returns the trigger (start) time of the Y array.
	dt returns the time interval between data points in the Y array.
	Y returns 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.

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

Note Although the MT Resample (Complex Cluster) VI can be used to downsample a complex waveform, the MT Decimate Oversampled Waveform VI is sometimes a more suitable choice because it does not apply filtering during the decimation process. Compared to the MT Fractional Resample VI, this VI has the following characteristics:

Does not introduce any additional phase shift (other than any specified nonzero offset)
Does not introduce transient effects associated with filter application
More computational efficiency and speed

previous page start next page