1 ## Author: Paul Kienzle <pkienzle@users.sf.net> (2004)
2 ## This program is granted to the public domain.
4 ## flattopwin(L, [periodic|symmetric])
6 ## Return the window f(w):
8 ## f(w) = 1 - 1.93 cos(2 pi w) + 1.29 cos(4 pi w)
9 ## - 0.388 cos(6 pi w) + 0.0322cos(8 pi w)
11 ## where w = i/(L-1) for i=0:L-1 for a symmetric window, or
12 ## w = i/L for i=0:L-1 for a periodic window. The default
13 ## is symmetric. The returned window is normalized to a peak
16 ## This window has low pass-band ripple, but high bandwidth.
20 ## The main use for the Flat Top window is for calibration, due
21 ## to its negligible amplitude errors.
23 ## [1] Gade, S; Herlufsen, H; (1987) "Use of weighting functions in DFT/FFT
24 ## analysis (Part I)", Bruel & Kjaer Technical Review No.3.
26 function w = flattopwin (L, sym)
27 if nargin == 0 || nargin > 2
33 match = strmatch(sym,['periodic';'symmetric']);
35 error("window type must be periodic or symmetric");
43 x = 2*pi*[0:L-1]'/divisor;
44 w = (1-1.93*cos(x)+1.29*cos(2*x)-0.388*cos(3*x)+0.0322*cos(4*x))/4.6402;