TSA Periodogram VI

Owning Palette: Correlation and Spectral Analysis VIs

Requires: Advanced Signal Processing Toolkit

Computes the single-sided power spectral density (PSD) of a univariate time series using the periodogram method. The periodogram method is a fast Fourier transform (FFT) based method that estimates the PSD. Wire data to the Xt input to determine the polymorphic instance to use or manually select the instance.

Details  Examples

TSA Periodogram (Waveform)

	frequency bins specifies the number of frequency bins for which this VI computes the single-sided power spectral density PSD. The length of the single-sided PSD is (frequency bins/2+1). The default is 1024.
	Xt specifies the univariate time series.
	window specifies the time-domain window applied to the time series. Options include None (default), Hanning, Hamming, Blackman-Harris, Exact Blackman, Blackman, Flat Top, 4 Term B-Harris, 7 Term B-Harris, and Low Sidelobe.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	dB on? specifies whether this VI returns the PSD in decibels or in a linear scale. If dB on? is TRUE, this VI returns the PSD in decibels. If dB on? is FALSE, this VI returns the PSD in a linear scale. The default is TRUE.
	PSD returns information about the single-sided power spectral density (PSD). f0 returns the lower boundary, in hertz, of the frequency range. df returns the frequency increment, in hertz. S(f) returns the magnitude of the PSD at each frequency. The value of dB on? determines the unit of measurement for this parameter.
	unit returns the engineering unit of the PSD. You can specify an engineering unit for a time series by using the TSA Scale to EU VI.
	error out contains error information. This output provides standard error out functionality.

TSA Periodogram (Array)

	sampling rate specifies the sampling rate, in hertz, of the univariate time series Xt. The default is 1.
	frequency bins specifies the number of frequency bins for which this VI computes the single-sided power spectral density PSD. The length of the single-sided PSD is (frequency bins/2+1). The default is 1024.
	Xt specifies the univariate time series.
	window specifies the time-domain window applied to the time series. Options include None (default), Hanning, Hamming, Blackman-Harris, Exact Blackman, Blackman, Flat Top, 4 Term B-Harris, 7 Term B-Harris, and Low Sidelobe.
	error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
	dB on? specifies whether this VI returns the PSD in decibels or in a linear scale. If dB on? is TRUE, this VI returns the PSD in decibels. If dB on? is FALSE, this VI returns the PSD in a linear scale. The default is TRUE.
	PSD returns information about the single-sided power spectral density (PSD). f0 returns the lower boundary, in hertz, of the frequency range. df returns the frequency increment, in hertz. S(f) returns the magnitude of the PSD at each frequency. The value of dB on? determines the unit of measurement for this parameter.
	error out contains error information. This output provides standard error out functionality.

TSA Periodogram Details

This VI computes the PSD of a time series using the periodogram method according to the following equation:

where S(f) is the PSD of the time series. df is the frequency interval, which is computed as f_s/N. NBW is the noise power bandwidth of the window. N is the number of frequency bins. f_s is the sampling rate. Before computing the PSD, this VI wraps the original time series X_t to an N-point series X_t'.

Examples

Refer to the following VIs for examples of using the TSA Periodogram VI:

• Average PSD VI: labview\examples\Time Series Analysis\TSAGettingStarted
• Beam Crack Detection VI: labview\examples\Time Series Analysis\TSAApplications
• Power Spectral Density Estimation VI: labview\examples\Time Series Analysis\TSAGettingStarted