spectrum.welch (Signal Processing Toolbox)

Welch spectrum

Syntax

Hs = spectrum.welch
Hs = spectrum.welch(WindowName)
Hs = spectrum.welch({WindowName,winparam})
Hs = spectrum.welch(...,SegmentLength)
Hs = spectrum.welch(...,OverlapPercent)
Hs = spectrum.welch(...,FFTLength)

Description

Hs = spectrum.welch returns a default Welch spectrum object, Hs, that defines the parameters for Welch's averaged, modified periodogram spectral estimation method. The object uses these default values.

Property Name
Default Value
Description

WindowName
'Hamming',
SamplingFlag: symmetric

Window name string or 'User Defined' (see window for valid window names). If the window uses an optional property, it is set to the default value.

{WindowName,
winparam}

Cell array containing WindowName and optional window parameter
'Hamming',
SamplingFlag: symmetric
Cell array containing the window name string or 'User Defined' and, if used for the particular window, an optional parameter value. (See window for valid window names and for more information on each window, refer to its reference page.)

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.)

SegmentLength
64
Segment length

OverlapPercent
50%
Percent overlap between segments

FFTlength
'NextPow2'
String defining how the number of FFT points is determined. The default is the next power of 2 that is greater than the input length. Other valid values are 'InputLength' and 'UserDefined'. InputLength uses the length of the input signal as the FFT length. UserDefined uses the value provided via the psd method or dspopts object. See dspopts for an example.

Property Name	Default Value	Description
WindowName	'Hamming', `SamplingFlag: symmetric`	Window name string or `'User Defined'` (see `window` for valid window names). If the window uses an optional property, it is set to the default value.
{WindowName`,` `winparam}` Cell array containing WindowName and optional window parameter	'Hamming', `SamplingFlag: symmetric`	Cell array containing the window name string or `'User Defined'` and, if used for the particular window, an optional parameter value. (See `window` for valid window names and for more information on each window, refer to its reference page.) 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`.)
SegmentLength	`64`	Segment length
OverlapPercent	`50%`	Percent overlap between segments
FFTlength	'NextPow2'	String defining how the number of FFT points is determined. The default is the next power of 2 that is greater than the input length. Other valid values are `'InputLength'` and `'UserDefined'`. `InputLength` uses the length of the input signal as the FFT length. `UserDefined` uses the value provided via the `psd` method or `dspopts` object. See `dspopts` for an example.

Hs = spectrum.welch(WindowName) returns a spectrum object, Hs, using Welch's method with the specified window and the default values for all other parameters

Note Window names must be enclosed in single quotes, such as spectrum.welch('chebyshev',32,50) or spectrum.music({'chebyshev',60},32,50)

Hs = spectrum.welch({WindowName,winparam}) returns a spectrum object, Hs with the specified window and associated parameter.

Hs = spectrum.welch(...,SegmentLength) returns a spectrum object, Hs with the specified segment length.

Hs = spectrum.welch(...,OverlapPercent) returns a spectrum object, Hs with the specified percentage overlap between segments.

Hs = spectrum.welch(...,FFTLength) returns a spectrum object, Hs with the specified FFT length type.

Note See pwelch for more information on the Welch algorithm.

Examples

Define a cosine of 200 Hz, add noise and view its spectral content using the Welch algorithm.

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

spectrum.periodogram spectrum.yulear