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# sigwin.chebwin class

Package: sigwin

Construct Dolph-Chebyshev window object

## Description

sigwin.chebwin creates a handle to a Dolph–Chebyshev 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 Dolph-Chebyshev window is constructed in the frequency domain by taking samples of the window's Fourier transform:

$\stackrel{^}{W}\left(k\right)={\left(-1\right)}^{k}\frac{\mathrm{cos}\left[N{\mathrm{cos}}^{-1}\left[\beta \mathrm{cos}\left(\pi k/N\right)\right]\right]}{\mathrm{cosh}\left[N{\mathrm{cosh}}^{-1}\left(\beta \right)\right]}\text{ }0\le k\le N-1$

where

$\beta =\mathrm{cos}\left[1/N{\mathrm{cosh}}^{-1}\left({10}^{\alpha }\right)\right]$

$\alpha$ determines the level of the sidelobe attenuation. The level of the sidelobe attenuation is equal to $-20\alpha$. For example, 100 dB of attenuation results from setting $\alpha =5$

The discrete-time Dolph-Chebyshev window is obtained by taking the inverse DFT of $\stackrel{^}{W}\left(k\right)$ and scaling the result to have a peak value of 1.

## Construction

H = sigwin.chebwin returns a Dolph-Chebyshev window object H of length 64 with relative sidelobe attenuation of 100 dB.

H = sigwin.chebwin(Length) returns a Dolph–Chebyshev window object H of length Length with relative sidelobe attenuation of 100 dB. Length requires a positive integer. Entering a positive noninteger value for Length rounds the length to the nearest integer. A window length of 1 results in a window with a single value equal to 1.

H = sigwin.chebwin(Length,SidelobeAtten) returns a Dolph-Chebyshev window object with relative sidelobe attenuation of atten_param dB.

## Properties

 Length Dolph-Chebyshev window length. SidelobeAtten The attenuation parameter in dB. The attenuation parameter is a positive real number that determines the relative sidelobe attenuation of the window.

## Methods

 generate Generates Dolph-Chebyshev window info Display information about Dolph–Chebyshev window object winwrite Save Dolph-Chebyshev window object values 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 Dolph–Chebyshev window with 100 dB relative sidelobe attenuation:

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

Generate length N=128 Chebyshev window with 120 dB attenuation, return values, and write ASCII file:

```H=sigwin.chebwin(128,120);
% Return window with generate
win=generate(H);
% Write ASCII file in current directory
% with window values
winwrite(H,'chebwin_128_100')```

## References

Harris.F.J. "On the Use of Windows for Harmonic Analysis with the Discrete Fourier Transform." Proceedings of the IEEE®. Vol. 66, 1978, pp. 51–83.