Computes the estimated power and frequency around the peak frequency in the power spectrum of a time-domain signal.


icon

Inputs/Outputs

  • c1ddbl.png Power Spectrum (V^2 rms) —

    Power Spectrum is the power spectrum of a time domain signal. Power Spectrum is the output of the Auto Power Spectrum VI.

  • cdbl.png peak frequency (max) —

    peak frequency is the frequency, usually in hertz, of the frequency peak around which you want to estimate the frequency and power. The default is –1.

    If you do not wire this parameter, the VI automatically searches for the maximum peak in the power spectrum array and estimates the frequency and power around it.

  • cnclst.png window constants —

    window constants specifies the property constants of a window. If you apply a window to a time-domain signal to avoid spectral leakage when you compute the power spectrum of the signal, you can use window constants to compensate for the effect of the window you apply. The default values are set to those of the rectangular window (no window).

    window constants is usually the output of the Scaled Time Domain Window VI.

  • cdbl.png eq noise BW —

    eq noise BW is the equivalent noise bandwidth (ENBW) of the window that was used. The default is 1.0.

    You can use this value to divide a sum of individual power spectra of the power spectrum or to compute the power in a given frequency span.

  • cdbl.png coherent gain —

    coherent gain is the inverse of the scaling factor applied to the window. The default is 1.0.

  • cdbl.png df —

    df is the frequency interval of the power spectrum. The default is 1.0.

  • ci32.png span —

    span is the number of frequency lines (bins) around the peak to be included in the peak frequency and power estimation.

    The default is 7, which means that the power in three frequency lines before the peak frequency line, the peak frequency line itself, and three frequency lines after the peak are included in the estimation. This is adequate for most windows.

  • idbl.png est frequency peak —

    est frequency peak is the estimated frequency of the peak in the input Power Spectrum.

    est frequency peak is computed as for j = i – span/2, …i + span/2,

    where i = peak index, Power Spectrum (j) = power in bin j, and df = frequency bin width.

  • idbl.png est power peak —

    est power peak is the estimated power of the peak in the input Power Spectrum.

    est power peak is computed as for j = i – span/2, …i + span/2,

    where i = peak index, Power Spectrum (j) = power in bin j, and ENBW = equivalent noise bandwidth of the window.

    • With the Power & Frequency Estimate VI, you can achieve good frequency estimates for measured frequencies that lie between frequency lines on the spectrum. The Power & Frequency Estimate VI also makes corrections for the window function you use.

    Examples

    Refer to the following example files included with LabVIEW.

    • labview\examples\Signal Processing\Spectral Analysis\Power & Frequency Estimator.vi