Rational Resample VI

Owning Palette: Signal Operation VIs

Requires: Full Development System

Resamples the input signal X by interpolating X, passing the interpolated signal through an FIR filter, and decimating the filtered signal. Wire data to the X input to determine the polymorphic instance to use or manually select the instance.

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Use the pull-down menu to select an instance of this VI.

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Rational Resample (single channel, DBL)

anti-aliasing? specifies whether the input signal undergoes lowpass filtering when LabVIEW downsamples the signal. If anti-aliasing? is TRUE (default), this VI protects the resampled signal from aliasing. However, the computation requirements increase during resampling.
reset controls the initialization of resampling. The default is FALSE. The first time this VI runs or when reset is TRUE, LabVIEW initializes the internal states of the VI to zero and uses start index to determine when the resampling starts. The next time this VI runs and reset is FALSE, LabVIEW initializes the internal states to the final states from the previous call to this VI.

To process a large data sequence that consists of smaller blocks, set reset to TRUE for the first block and to FALSE for all the remaining blocks in continuous resampling.
X is the input real signal for resampling. The sampling interval of X is 1.
start index determines where the resampling starts for the first call to the VI or if reset is TRUE. Set the start index according to the signal after X is interpolated. start index must be greater than or equal to 0. The default is 0.
resample factor contains the interpolation factor and the decimation factor for resampling.
interpolation is the interpolation factor for resampling. The default is 1.
decimation is the decimation factor for resampling. The default is 1.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
FIR filter specifications specifies the minimum values this VI needs to specify the FIR filter.
alias rejection (dB) specifies the minimum attenuation level of signal components aliased after any resampling operation. The default is 120.
normalized bandwidth specifies the fraction of the new sampling rate that is not attenuated. The default is 0.4536.
Y returns the resampled signal. The sampling interval of Y is decimation/interpolation.
t0 returns the time instance for the first sample of each signal in Y.
error out contains error information. This output provides standard error out functionality.

Rational Resample (single channel, CDB)

anti-aliasing? specifies whether the input signal undergoes lowpass filtering when LabVIEW downsamples the signal. If anti-aliasing? is TRUE (default), this VI protects the resampled signal from aliasing. However, the computation requirements increase during resampling.
reset controls the initialization of resampling. The default is FALSE. The first time this VI runs or when reset is TRUE, LabVIEW initializes the internal states of the VI to zero and uses start index to determine when the resampling starts. The next time this VI runs and reset is FALSE, LabVIEW initializes the internal states to the final states from the previous call to this VI.

To process a large data sequence that consists of smaller blocks, set reset to TRUE for the first block and to FALSE for all the remaining blocks in continuous resampling.
X is the input complex signal for resampling. The sampling interval of X is 1.
start index determines where the resampling starts for the first call to the VI or if reset is TRUE. Set the start index according to the signal after X is interpolated. start index must be greater than or equal to 0. The default is 0.
resample factor contains the interpolation factor and the decimation factor for resampling.
interpolation is the interpolation factor for resampling. The default is 1.
decimation is the decimation factor for resampling. The default is 1.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
FIR filter specifications specifies the minimum values this VI needs to specify the FIR filter.
alias rejection (dB) specifies the minimum attenuation level of signal components aliased after any resampling operation. The default is 120.
normalized bandwidth specifies the fraction of the new sampling rate that is not attenuated. The default is 0.4536.
Y returns the resampled signal. The sampling interval of Y is decimation/interpolation.
t0 returns the time instance for the first sample of each signal in Y.
error out contains error information. This output provides standard error out functionality.

Rational Resample (multi-channel, DBL)

anti-aliasing? specifies whether the input signal undergoes lowpass filtering when LabVIEW downsamples the signal. If anti-aliasing? is TRUE (default), this VI protects the resampled signal from aliasing. However, the computation requirements increase during resampling.
reset controls the initialization of resampling. The default is FALSE. The first time this VI runs or when reset is TRUE, LabVIEW initializes the internal states of the VI to zero and uses start index to determine when the resampling starts. The next time this VI runs and reset is FALSE, LabVIEW initializes the internal states to the final states from the previous call to this VI.

To process a large data sequence that consists of smaller blocks, set reset to TRUE for the first block and to FALSE for all the remaining blocks in continuous resampling.
X contains the input real signals for resampling. Each row of X contains an input signal. All the signals have the same length. The sampling interval of each signal in X is 1.
start index determines where the resampling starts for the first call to the VI or if reset is TRUE. Set the start index according to the signal after X is interpolated. start index must be greater than or equal to 0. The default is 0.
resample factor contains the interpolation factor and the decimation factor for resampling.
interpolation is the interpolation factor for resampling. The default is 1.
decimation is the decimation factor for resampling. The default is 1.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
FIR filter specifications specifies the minimum values this VI needs to specify the FIR filter.
alias rejection (dB) specifies the minimum attenuation level of signal components aliased after any resampling operation. The default is 120.
normalized bandwidth specifies the fraction of the new sampling rate that is not attenuated. The default is 0.4536.
Y returns the resampled signals. Each row of Y contains a resampled signal that corresponds to the input signal in the same row of X. All the resampled signals have the same length. The sampling interval of each signal is decimation/interpolation.
t0 returns the time instance for the first sample of each signal in Y.
error out contains error information. This output provides standard error out functionality.

Rational Resample (multi-channel, CDB)

anti-aliasing? specifies whether the input signal undergoes lowpass filtering when LabVIEW downsamples the signal. If anti-aliasing? is TRUE (default), this VI protects the resampled signal from aliasing. However, the computation requirements increase during resampling.
reset controls the initialization of resampling. The default is FALSE. The first time this VI runs or when reset is TRUE, LabVIEW initializes the internal states of the VI to zero and uses start index to determine when the resampling starts. The next time this VI runs and reset is FALSE, LabVIEW initializes the internal states to the final states from the previous call to this VI.

To process a large data sequence that consists of smaller blocks, set reset to TRUE for the first block and to FALSE for all the remaining blocks in continuous resampling.
X contains the input complex signals for resampling. Each row of X contains an input signal. All the signals have the same length. The sampling interval of each signal is 1.
start index determines where the resampling starts for the first call to the VI or if reset is TRUE. Set the start index according to the signal after X is interpolated. start index must be greater than or equal to 0. The default is 0.
resample factor contains the interpolation factor and the decimation factor for resampling.
interpolation is the interpolation factor for resampling. The default is 1.
decimation is the decimation factor for resampling. The default is 1.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
FIR filter specifications specifies the minimum values this VI needs to specify the FIR filter.
alias rejection (dB) specifies the minimum attenuation level of signal components aliased after any resampling operation. The default is 120.
normalized bandwidth specifies the fraction of the new sampling rate that is not attenuated. The default is 0.4536.
Y returns the resampled signals. Each row of Y contains a resampled signal that corresponds to the input signal in the same row of X. All the resampled signals have the same length. The sampling interval of each signal is decimation/interpolation.
t0 returns the time instance for the first sample of each signal in Y.
error out contains error information. This output provides standard error out functionality.

Rational Resample Details

The following steps describe the rational resampling process. Each step corresponds to a numbered section of the following image.

  1. Input signal X for resampling. The time interval between two adjacent samples is 1.
  2. Insert zeros between every two adjacent samples to upsample X by the interpolation factor. Let X1 represent the interpolated signal.
  3. Using a FIR filter, filter X1at the start index to obtain the first output sample. The elements outside the range of the interpolated signal equal zero.
  4. Move the filter to the position start index + decimation and filter again to obtain the second output sample.
  5. Repeat step 4, adding each new decimation value until there are not enough samples in X1 for filtering. Store the final samples to internal states and wait for the next signal block. The time interval between two adjacent samples in an output signal is equal to decimation / interpolation. t0 specifies the time of the first output sample.

Related Information

Selecting the Instance of a Polymorphic VI Manually

Passband Ripple and Stopband Attenuation

Example

Refer to the Rational Resampling VI in the labview\examples\Signal Processing\Signal Operation directory for an example of using the Rational Resample VI.

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