spectrum.periodogram (Signal Processing Toolbox)

Periodogram spectrum

Syntax

Hs = spectrum.periodogram
Hs = spectrum.periodogram(winname)
Hs = spectrum.periodogram({winname,winparameter})
Hs = spectrum.periodogram(...,FFTLength)

Description

Hs = spectrum.periodogram returns a default periodogram spectrum object, Hs, that defines the parameters for theperiodogram spectral estimation method. This default object uses a rectangular window and a default FFT length equal to the next power of 2 (NextPow2) that is greater than the input length.

Hs = spectrum.periodogram(winname) returns a spectrum object, Hs, that uses the specified window. If the window uses an optional associated window parameter, it is set to the default value. This object uses the default FFT length.

Hs = spectrum.periodogram({winname,winparameter}) returns a spectrum object, Hs, that uses the specified window and optional associated window parameter, if any. You specify the window and window parameter in a cell array with a windowname string and the parameter value. This object uses the default FFT length.

Valid windowname strings are any valid window in the Signal Processing Toolbox or a user-defined window. Refer to the corresponding window function page for window parameter information.

You can use set to change the value of the additional parameter or to define the MATLAB expression and parameters for a user-defined window (see spectrum for information on using set).

Note Window names must be enclosed in single quotes, such as

spectrum.periodogram('tukey') or
spectrum.periodogram({'tukey',0.7})

Hs = spectrum.periodogram(...,FFTLength) returns a spectrum object, Hs that uses the specified way of determining the FFTLength. Valid values of the FFTLength string are as follows.

FFTLength string
Description

'InputLength'
Use the length of the input signal as the FFT length

'NextPow2'
Use the next power of 2 greater than the input signal length as the FFT length. This is the default value.

'UserDefined'
Use the FFT length provided as an input to the psd method or via a dspopts object. See dspopts for an example.

FFTLength string	Description
`'InputLength'`	Use the length of the input signal as the FFT length
`'NextPow2'`	Use the next power of 2 greater than the input signal length as the FFT length. This is the default value.
`'UserDefined'`	Use the FFT length provided as an input to the `psd` method or via a `dspopts` object. See `dspopts` for an example.

Note See periodogram for more information on the periodogram algorithm.

Examples

Define a cosine of 200 Hz, add noise and view its spectral content using the periodogram spectral estimation technique.

Fs=1000;
t=0:1/Fs:.3;
x=cos(2*pi*t*200)+randn(size(t));
Hs=spectrum.periodogram;          % Use default values
psd(Hs,x,'Fs',Fs)

spectrum.music spectrum.welch