# 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 (MATLAB) in the MATLAB® Programming Fundamentals documentation.

## Examples

expand all

Generate a Dolph-Chebyshev window of length N = 16. Specify a relative sidelobe attenuation of 40 dB. Return the window values as a column vector. Show information about the window object. Display the window.

```H = sigwin.chebwin(16,40); win = generate(H)```
```win = 0.1138 0.1964 0.3319 0.4926 0.6613 0.8163 0.9353 1.0000 1.0000 0.9353 ```
`wininfo = info(H)`
```wininfo = 4x26 char array 'Chebyshev Window ' '---------------- ' 'Length : 16' 'Sidelobe Attenuation : 40' ```
`wvtool(H)`

## 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.