Note:
The use of 
sigwin.blackman
creates a handle to a Blackman
window object for use in spectral analysis and FIR filtering by the
window method. Object methods enable workspace import and ASCII file
export of the window values.
The following equation defines the Blackman window of length N
:
$$w(n)=0.420.5\mathrm{cos}\frac{2\pi n}{N1}+0.08\mathrm{cos}\frac{4\pi n}{N1},\text{\hspace{1em}}0\le n\le M1$$
where M
is N/2
for N
even and (N+1)/2
for N
odd.
In the symmetric case, the second half of the Blackman window $$M\le n\le N1$$ is obtained by flipping the first half around the midpoint. The symmetric option is the preferred method when using a Blackman window in FIR filter design.
The periodic Blackman window is constructed by extending the
desired window length by one sample to N+1
, constructing a symmetric window, and removing the last sample.
The periodic version is the preferred method when using a Blackman
window in spectral analysis because the discrete Fourier transform
assumes periodic extension of the input vector.
H = sigwin.blackman
returns a Blackman
window object H
of length 64 with symmetric sampling.
H = sigwin.blackman(
returns a Blackman window object Length
)H
of length Length
with symmetric sampling. Length
requires a positive integer. Entering a positive
noninteger value for Length
rounds the
length to the nearest integer. Entering a 1 for Length
results in a window with a single value of 1.
H = sigwin.blackman(
returns a Blackman
window object Length
,SamplingFlag
)H
with sampling Sampling_Flag
. The Sampling_Flag
can be either 'symmetric'
or 'periodic'
.

Blackman window length. Must be a positive integer. Entering
a positive noninteger value for 


generate  Generates Blackman window 
info  Display information about Blackman window object 
winwrite  Save Blackman window in ASCII file 
Handle. To learn how this affects your use of the class, see Copying Objects in the MATLAB^{®} Programming Fundamentals documentation.
Default length N = 64
symmetric Blackman
window:
H = sigwin.blackman; wvtool(H)
Generate length N = 128
periodic Blackman
window, return values, and write ASCII file:
H = sigwin.blackman(128,'periodic'); % Return window with generate win = generate(H); % Write ASCII file in current directory % with window values winwrite(H,'blackman_128')
Oppenheim, Alan V., and Ronald W. Schafer. DiscreteTime Signal Processing. Upper Saddle River, NJ: Prentice Hall, 1989.