# Documentation

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# sigwin.chebwin class

Package: sigwin

Construct Dolph-Chebyshev window object

## Description

 Note:   The use of `sigwin.chebwin` is not recommended. Use `chebwin` instead.

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

## How To

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