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# flattopwin

Flat Top weighted window

## Syntax

w = flattopwin(L)
w = flattopwin(L,sflag)

## Description

Flat Top windows have very low passband ripple (< 0.01 dB) and are used primarily for calibration purposes. Their bandwidth is approximately 2.5 times wider than a Hann window.

w = flattopwin(L) returns the L-point symmetric flat top window in column vector w.

w = flattopwin(L,sflag) returns the L-point symmetric flat top window using sflag window sampling, where sflag is either 'symmetric' or 'periodic'. The 'periodic' flag is useful for DFT/FFT purposes, such as in spectral analysis. The DFT/FFT contains an implicit periodic extension and the periodic flag enables a signal windowed with a periodic window to have perfect periodic extension. When 'periodic' is specified, flattopwin computes a length L+1 window and returns the first L points. When using windows for filter design, the 'symmetric' flag should be used.

## Examples

Create a 64-point, symmetric Flat Top window and view the window using WVTool:

```w = flattopwin(64);
wvtool(w);
```

## More About

expand all

### Algorithms

Flat top windows are summations of cosines. The coefficients of a flat top window are computed from the following equation

where and elsewhere and the window length is L = N +1. The coefficient values are

CoefficientValue
a00.21557895
a10.41663158
a20.277263158
a30.083578947
a40.006947368

## References

[1] D'Antona, Gabriele. and A. Ferrero, Digital Signal Processing for Measurement Systems, New York: Springer Media, Inc., 2006, pp. 70–72.

[2] Gade, Svend and H. Herlufsen, "Use of Weighting Functions in DFT/FFT Analysis (Part I)," Brüel & Kjær, Windows to FFT Analysis (Part I) Technical Review, No. 3, 1987, pp. 19-21.

## See Also

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