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psd_welch (MathScript RT Module Function)

LabVIEW 2012 MathScript RT Module Help

Edition Date: June 2012

Part Number: 373123C-01

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Owning Class: spectral analysis

Requires: MathScript RT Module

Syntax

psd_welch(x)

psd_welch(x, win)

psd_welch(x, win, noverlap)

psd_welch(x, win, noverlap, fftsize)

psd_welch(x, win, noverlap, range)

psd_welch(x, win, noverlap, fftsize, fs)

psd_welch(x, win, noverlap, fftsize, range)

psd_welch(x, win, noverlap, fftsize, fs, range)

Pxx = psd_welch(x)

Pxx = psd_welch(x, win)

Pxx = psd_welch(x, win, noverlap)

Pxx = psd_welch(x, win, noverlap, fftsize)

Pxx = psd_welch(x, win, noverlap, range)

Pxx = psd_welch(x, win, noverlap, fftsize, fs)

Pxx = psd_welch(x, win, noverlap, fftsize, range)

Pxx = psd_welch(x, win, noverlap, fftsize, fs, range)

[Pxx, w] = psd_welch(x)

[Pxx, w] = psd_welch(x, win)

[Pxx, w] = psd_welch(x, win, noverlap)

[Pxx, w] = psd_welch(x, win, noverlap, fftsize)

[Pxx, w] = psd_welch(x, win, noverlap, range)

[Pxx, w] = psd_welch(x, win, noverlap, fftsize, range)

[Pxx, f] = psd_welch(x, win, noverlap, fftsize, fs)

[Pxx, f] = psd_welch(x, win, noverlap, fftsize, fs, range)

Legacy Name: pwelch

Description

Uses the Welch method to calculate the power spectral density of the input signal. If you do not request an output, this function plots the power spectral density in the current plot window.

Examples

Inputs

Name Description
x Specifies the input signal sequence. x is a real or complex vector.
win Specifies the window to apply to each segment of x. The length of win determines the segment length into which LabVIEW divides x. win can be a vector that represents the window coefficients or an integer that represents a Hamming window with a length of win. The default is a Hamming window where LabVIEW divides x into eight sections.
noverlap Specifies the number of data elements that overlap between adjacent segments of data. noverlap must be less than the length of win. The default is the length that results in an overlap of half the data elements between adjacent segments.
fftsize Specifies the length of the FFT to perform on each segment of the data. The default is the next power of 2 greater than the length of each segment of x if this number is greater than 256. Otherwise, the default is 256.
fs Specifies the sampling frequency of the input sequence in Hz. If you specify fs, LabVIEW returns the output frequencies in Hz. Otherwise, LabVIEW returns the output frequencies in radians per sample.
range Specifies the range of the power spectral density. range is a string that accepts the following values.

'onesided' (default) LabVIEW returns the single-sided power spectral density.
'twosided' LabVIEW returns the double-sided power spectral density.

Outputs

Name Description
Pxx Returns the power spectral density of the input signal x. If x is real and range is 'onesided', the length of Pxx is fftsize / 2 + 1 for an even fftsize and (fftsize + 1) / 2 for an odd fftsize. Otherwise, the length of Pxx is fftsize.
w Returns the frequencies in radians per sample at the points where LabVIEW evaluates Pxx.
f Returns the frequencies in Hz at the points where LabVIEW evaluates Pxx.

Details

The following table lists the support characteristics of this function.

Supported in the LabVIEW Run-Time Engine Yes (if you request output)
Supported on RT targets Yes (if you request output)
Suitable for bounded execution times on RT Not characterized

Examples

fs = 1000;
t = 0:1/fs:0.2;
fftsize = 1024;
noise = randnormal(size(t));
x = sin(2*pi*100*t) + cos(2*pi*250*t) + noise;
win = win_hann2(64);
noverlap = 32;
Pxx = psd_welch(x, win, noverlap, fftsize, fs);

Related Topics

psd_burg
psd_covar
psd_mcovar
psd_periodogram
psd_yule
pspec_eign
pspec_music


 

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