Time Series Spectrum Express 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 with the periodogram, Welch, autoregressive (AR) modeling, autoregressive-moving average (ARMA) modeling, or multiple signal classification (MUSIC) method.

Dialog Box Options

Block Diagram Inputs

Block Diagram Outputs

Dialog Box Options

Parameter	Description
Data Source	Specifies whether this Express VI reads data from a block diagram input terminal or from a file. From terminal specifies that this Express VI reads data from a block diagram input terminal. From file specifies that this Express VI reads data from a file. This Express VI can read data from waveform, WAV, or TXT files. The valid format of a TXT data file is a file that contains only a 1D real array.
File Path Configuration	Contains the following options: File path—Specifies and displays the path to the file from which this Express VI reads data. This option is available only when you select From file in the Data Source section. Prompt to choose a file each time this VI runs—Specifies whether this Express VI displays a dialog box that prompts you to select a file each time this Express VI runs. This option is available only when you select the From file option in the Data Source section.
Type	Specifies the spectrum type. Options include Periodogram Spectrum (default), Welch Spectrum, MUSIC Spectrum, AR Spectrum, and ARMA Spectrum.
Algorithm Settings	Contains the following options: Frequency bins—Specifies the number of frequency bins for which this VI computes the power spectral density. The length of the resulting single-sided PSD is Frequency bins/2+1. Window—Specifies the time-domain window you apply to the time series. Options include Hanning, Hamming, Blackman-Harris, Exact Blackman, Blackman, Flat Top, 4 Term B-Harris, 7 Term B-Harris, and Low Sidelobe. This option is available only when you select Periodogram Spectrum, Welch Spectrum or MUSIC Spectrum in Type. Window length—Specifies the length of the window. A large window size leads to a small variance and a large bias of the power spectral density, and vice versa. This option is available only when you select Welch Spectrum or MUSIC Spectrum in Type. Overlap—Specifies the overlap of the moving window applied to a time series as a percentage. This option is available only when you select Welch Spectrum or MUSIC Spectrum in Type. Subspace—Specifies the percentage of the noise subspace in the whole space, that is, the union of the signal subspace and the noise subspace. This option is available only when you select MUSIC Spectrum in Type. Weight—Specifies the weighting method used to estimate the power spectral density. Options include Eigenvector (eigenvalue weighting) and None (no weighting). This option is available only when you select MUSIC Spectrum in Type. AR order—Specifies the AR order of the autoregressive or autoregressive-moving average model. This option is available only when you select AR Spectrum or ARMA Spectrum in Type. Method of AR Model—Specifies the method to use in estimating the autoregressive model. Options include Forward-Backward (default), Least-Squares, Yule-Walker, Burg-Lattice, and Geometric-Lattice. This option is available only when you select AR Spectrum in Type. MA order—Specifies the MA order of the autoregressive-moving average model. The value of MA order must be greater than zero. This option is available only when you select ARMA Spectrum in Type. Method of ARMA—Specifies the method to use in estimating the autoregressive-moving average model. Options include Yule-Walker (default), High order AR, and Polynomial. This option is available only when you select ARMA Spectrum in Type.
Signal and Window	Displays the signal and window. Contains the following option: Display window—Specifies to display the windows that you apply to the time series. This option is available only when you select Periodogram Spectrum, Welch Spectrum, or MUSIC Spectrum in Type.
Spectrum	Contains the following options: dB—Specifies to return the results in decibels. The default is TRUE. Spectrum—Displays the power spectral density of a time series.

Block Diagram Inputs

Parameter	Description
error in (no error)	Describes error conditions that occur before this node runs.
Xt	Specifies the time series. Xt is available only when you select From terminal in Data Source.
File path	Specifies the file path of the data you want to load. This input is available only when you select the From file option in the Data Source section.

Block Diagram Outputs

Parameter	Description
error out	Contains error information. This output provides standard error out functionality.
PSD	Returns information about the single-sided power spectral density, such as the magnitude and the frequency increment.
unit	Returns the selected engineering unit of the estimated power spectral density.

This Express VI operates similarly to the following VIs and functions:

TSA Periodogram
TSA Welch
TSA AR Spectrum
TSA ARMA Spectrum
TSA MUSIC