Subset and Resample (Frequency Domain)

LabVIEW SignalExpress

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Subset and Resample (Frequency Domain)

Extracts a subset of an input signal using the Start frequency and Subset length you specify or resamples an input signal using the frequency interval (df) you specify. If you specify a larger df, Subset and Resample downsamples the signal. If you specify a smaller df, Subset and Resample upsamples the signal.

ParameterDescription
Input SignalDisplays the input frequency-domain signal to be scaled.
  • Displayed signal—Specifies the signal(s) to display in the preview graph(s). This option appears only when you select a group of signals for the input.
    Note  If the input signals include scalar values that depend on the values of input waveform signals, you cannot specify to display all signals in the preview graph(s).
Processed SignalDisplays the processed signal.
InputContains the following option:
  • Input signal—Specifies the analog waveform for the step.
ConfigurationContains the following options:
  • Subset Setup—Contains the following options:
    • Extract subset—Specifies whether to extract a frequency subset of the signal using the Start frequency and Subset length you specify.
    • Start frequency—Specifies the start frequency of the subset signal.
    • Subset length—Specifies the frequency span of the subset signal.
  • Resampling Setup—Contains the following options:
    • Resample—Resamples the entire signal or subset you select.
    • Unwrap phase—Specifies if the phase of the output signal is unwrapped.
    • Open interval—Specifies if the subset is an open or closed interval. For example, if an input waveform contains 3 data elements at t={0, dt, 2dt}, an open interval defines the waveform as extending over the time interval 0≤t<2dt, and a closed interval defines the waveform as extending over the time interval 0≤t<3dt. Place a checkmark in this checkbox to specify an open interval.
    • Interpolation type—Contains the following options:
      • Coerce—Sets each output sample value to equal the input sample value that is closest to it in frequency.
      • Linear—Sets each output sample value to be a linear interpolation between the two input samples that are closest to it in frequency.
      • Spline—Uses the spline interpolation algorithm to compute the resampled values.
      • Filter based—Uses an interpolation method based on the convolution of the signal with a finite impulse response (FIR) filter.
    • df—Specifies the frequency resolution of the resampled frequency-domain signal. The default is 0.
Filter SetupAvailable when you select Filter based from Interpolation type. Contains the following option:
  • FIR Filter Specification—Contains the following options:
    • Normalized bandwidth—The normalized cut-off frequency of the FIR filter to use. The default is 0.4000.
    • Alias rejection (dB)—The minimum stopband attenuation of the FIR filter to use. The default is 80 dB.
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