Multiplies a series with a 3 term Blackman window.
BLACKMAN(series, ampflag, "sym")
series 
 
A series or array. 

ampflag 
 
Optional. An integer, the amplitude correction flag:


"sym" 
 
Optional. A string, the symmetry flag:

BLACKMAN(N, ampflag, "sym")
N 
 
An integer, the length of the window. 

ampflag 
 
Optional. An integer, the amplitude correction flag:


"sym" 
 
Optional. A string, the symmetry flag:

A series or array.
W1: gsin(1000, .001, 45)
W2: spectrum(blackman(W1))
W3: spectrum(blackman(W1, 1))
The MAX of W2 == 0.419 and the MAX of W3 == 1.0. The amplitude of the spectrum in W3 has been corrected to take into account amplitude effects of the symmetric 3 term Blackman window.
where n is the n^{th} point (1 <= n <= N) and N is the number of points to generate.
W4: blackman(1000, "periodic")
Creates a 1000 point periodic Blackman window that conforms to the ISO 184311 standard.
where n is the n^{th} point (1 <= n <= N) and N is the number of points to generate.
If ampflag == 1, the correction factor is the mean of the spectral window. This assures that the spectrum of a sinusoid of amplitude A has a peak of A.
If ampflag == 2, the correction is applied as follows:
w = blackman(s) * rms(s) / rms(blackman(s))
This assures that:
sqrt(area(psd(w))) == rms(s) approximately
If ampflag == 3, the correction is applied as follows:
w = winfun(s) / sqrt(mean(win * win)
where win is the windowing function.
The "sym" flag controls the window symmetry as follows:
"Symmetric" sets the last point to be the same value as the first point. For an N point symmetric window, a N1 point periodic window is effectively created and the N^{th} point is set to the same value as the first point.
"Periodic" or "iso" creates a periodic window function useful in spectrum analysis applications. "Periodic" or "iso" conforms to the ISO 184311 standard for windowing functions.
The Hamming, Hanning, Flattop and Blackman windows are part of the family of cosine window functions. The ISO 184311 standard periodic form of these windowing functions are defined by:
where K is the number of window coefficients and N is the length of the window. The symmetric form of the window can be constructed by setting N to
For the Blackman window:
See GBLACKMAN to generate a Blackman window.
See BLACKMANHARRIS to multiply a series with a 4 term BlackmanHarris window.