Estimate crosspower spectrum density
Estimation / Power Spectrum Estimation
dspspect3
The Cross Spectrum Estimator block outputs the frequency crosspower spectrum density of two real or complex input signals, x and y, via Welch’s method of averaged modified periodograms. The input signals must be of the same size and data type.
The Cross Spectrum Estimator block computes the current power spectrum estimate by averaging the last N power spectrum estimates, where N is the number of spectral averages defined in Number of spectral averages. The block buffers the input data into overlapping segments. You can set the length of the data segment and the amount of data overlap through the parameters set in the block dialog box. The block computes the power spectrum based on the parameters set in the block dialog box.
Each column of the input signal is treated as a separate channel. If the input is a twodimensional signal, the first dimension represents the channel length (or frame size) and the second dimension represents the number of channels. If the input is a onedimensional signal, then it is interpreted as a single channel.
This block brings the capabilities of the dsp.CrossSpectrumEstimator
System
object™ to
the Simulink^{®} environment.
For information on the algorithm used by the Cross Spectrum
Estimator block, see the Algorithms section of dsp.CrossSpectrumEstimator
.
Source of the window length value. You can set this parameter to:
Same as input frame length
(default)
— Window length is set to the frame size of the input.
Specify on dialog
—
Window length is the value specified in Window length.
This parameter is nontunable.
Length of the window, in samples, used to compute the spectrum
estimate, specified as a positive integer scalar greater than 2
.
This parameter applies when you set Window length source to Specify
on dialog
. The default is 1024
. This
parameter is nontunable.
Percentage of overlap between successive data windows, specified
as a scalar in the range [0, 100
). The default
is 0
. This parameter is nontunable.
Number of spectral averages, specified as a positive integer
scalar. The crossspectrum estimator computes the current power spectrum
estimate by averaging the last N power spectrum
estimates, where N is the number of spectral averages
defined in Number of spectral averages. The default
is 1
. This parameter is nontunable.
Source of the FFT length value. You can set this parameter to:
Auto
(default) —
FFT length is set to the frame size of the input.
Property
— FFT length
is the value specified in FFT length.
This parameter is nontunable.
Length of the FFT used to compute the spectrum estimates, specified
as a positive integer scalar. This parameter applies when you set FFT
length source to Property
. The
default is 1024
. This parameter is nontunable.
Window function for the crossspectrum estimator, specified
as one of Chebyshev
 Flat
Top
 Hamming
 Hann
 Kaiser
 Rectangular
.
The default is Hann
. This parameter is
nontunable.
Side lobe attenuation of the window, specified as real positive
scalar. This parameter applies when you set Window function to Chebyshev
or Kaiser
.
The default is 60
. This parameter is nontunable.
Frequency range of the crossspectrum estimator. You can set this parameter to:
centered
(default) —
The crossspectrum estimator computes the centered twosided spectrum
of complex or real input signals, x and y.
The length of the crossspectrum estimate is equal to the FFT length.
The spectrum estimate is computed over the frequency range [SampleRate/2
SampleRate/2]
when the FFT length is even and [SampleRate/2
SampleRate/2]
when FFT length is odd.
onesided
— The crossspectrum
estimator computes the onesided spectrum of real input signals, x and y.
When the FFT length, NFFT is even, length of the
crossspectrum estimate is (NFFT/ 2
)
+ 1
, and is computed over the frequency range [0
SampleRate/2]
. When the FFT length, NFFT is
odd, length of the crossspectrum estimate is (NFFT +
1)/ 2
, and is computed over the frequency range [0
SampleRate/2]
.
twosided
— The crossspectrum
estimator computes the twosided spectrum of complex or real input
signals, x and y. The length
of the crossspectrum estimate is equal to the FFT length. The spectrum
estimate is computed over the frequency range [0 SampleRate]
,
where SampleRate
is the sample rate of the input
signal.
This parameter is nontunable.
When you select this check box, the block’s sample rate is computed as N/Ts, where N is the frame size of the input signal, and Ts is the sample time of the input signal. When you clear this check box, the block sample rate is the value specified in Sample rate (Hz). By default, this check box is selected.
Sample rate of the input signal, specified as a positive scalar
value. The default is 44100
. This parameter applies
when you clear the Inherit sample rate from input check
box. This parameter is nontunable.
Type of simulation to run. You can set this parameter to:
Code generation
(default)
Simulate model using generated C code. The first time you run
a simulation, Simulink generates C code for the block. The C
code is reused for subsequent simulations, as long as the model does
not change. This option requires additional startup time but provides
faster simulation speed than Interpreted execution
.
Interpreted execution
Simulate model using the MATLAB^{®} interpreter. This
option shortens startup time but has slower simulation speed than Code
generation
.
Port  Supported Data Types 

Input 

Output 

[1] Hayes, Monson H. Statistical Digital Signal Processing and Modeling. Hoboken, NJ: John Wiley & Sons, 1996.
[2] Kay, Steven M. Modern Spectral Estimation: Theory and Application. Englewood Cliffs, NJ: Prentice Hall, 1999.
[3] Stoica, Petre, and Randolph L. Moses. Spectral Analysis of Signals. Englewood Cliffs, NJ: Prentice Hall, 2005.
[4] Welch, P. D. ''The Use of Fast Fourier Transform for the Estimation of Power Spectra: A Method Based on Time Averaging Over Short Modified Periodograms''. IEEE Transactions on Audio and Electroacoustics. Vol. 15, No. 2, June 1967, pp. 70–73.