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# sigwin.blackmanharris class

Package: sigwin

Construct Blackman–Harris window object

## Description

sigwin.blackmanharris creates a handle to a Blackman-Harris 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 symmetric Blackman-Harris window of length N:

$w\left(n\right)={a}_{0}-{a}_{1}\mathrm{cos}\left(\frac{2\pi n}{N-1}\right)+{a}_{2}\mathrm{cos}\left(\frac{4\pi n}{N-1}\right)-{a}_{3}\mathrm{cos}\left(\frac{6\pi n}{N-1}\right)\text{ }0\le n\le N-1$

The following equation defines the periodic Blackman-Harris window of length N:

$w\left(n\right)={a}_{0}-{a}_{1}\mathrm{cos}\left(\frac{2\pi n}{N}\right)+{a}_{2}\mathrm{cos}\left(\frac{4\pi n}{N}\right)-{a}_{3}\mathrm{cos}\left(\frac{6\pi n}{N}\right)\text{ }0\le n\le N-1$

The following table lists the coefficients:

CoefficientValue
a00.35875
a10.48829
a20.14128
a30.01168

## Construction

H = sigwin.blackmanharris returns a Blackman-Harris window object H of length 64.

H = sigwin.blackmanharris(Length) returns a Blackman-Harris window object H of length Length. Length must be 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.

## Properties

 Length Blackman-Harris window length. The window 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. SamplingFlag The type of window returned as one of 'symmetric' or 'periodic'. The default is 'symmetric'. A symmetric window exhibits perfect symmetry between halves of the window. Setting the SamplingFlag property to 'periodic' results in a N-periodic window. The equations for the Blackman-Harris window differ slightly based on the value of the SamplingFlag property. See Description for details.

## Methods

 generate Generates Blackman–Harris window info Display information about Blackman–Harris window object winwrite Save Blackman–Harris window in ASCII file

## Copy Semantics

Handle. To learn how copy semantics affect your use of the class, see Copying Objects in the MATLAB® Programming Fundamentals documentation.

## Examples

Default length N=64 Blackman-Harris window:

```H=sigwin.blackmanharris;
wvtool(H); ```

Generate length N=128 periodic Blackman-Harris window, return values, and write ASCII file:

```H=sigwin.blackmanharris(128);
H.SamplingFlag = 'periodic';
% Return window with generate
win=generate(H);
% Write ASCII file in current directory
% with window values
winwrite(H,'blackmanharris_128')```

## References

Harris, F. J. "On the Use of Windows for Harmonic Analysis with the Discrete Fourier Transform," Proceedings of the IEEE®.. Vol. 66, 1978.