Flat Top weighted window
w = flattopwin(L)
w = flattopwin(L,sflag)
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,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.
Create a 64-point, symmetric Flat Top window and view the window using WVTool:
w = flattopwin(64); wvtool(w);
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
 D'Antona, Gabriele. and A. Ferrero, Digital Signal Processing for Measurement Systems, New York: Springer Media, Inc., 2006, pp. 70–72.
 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.