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author | pkienzle |
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date | Wed, 10 Oct 2001 19:54:49 +0000 |
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children | 2ac2777b30bc |
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## Copyright (C) 1995, 1996, 1997 Kurt Hornik ## ## This program is free software; you can redistribute it and/or modify ## it under the terms of the GNU General Public License as published by ## the Free Software Foundation; either version 2, or (at your option) ## any later version. ## ## This program is distributed in the hope that it will be useful, but ## WITHOUT ANY WARRANTY; without even the implied warranty of ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU ## General Public License for more details. ## ## You should have received a copy of the GNU General Public License ## along with this file. If not, write to the Free Software Foundation, ## 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. ## usage: kaiser (n, beta) ## ## Returns the filter coefficients of the n-point Kaiser window with ## parameter beta. ## ## For the definition of the Kaiser window, see A. V. Oppenheim & ## R. W. Schafer, "Discrete-Time Signal Processing". ## ## The continuous version of width n centered about x=0 is: ## ## besseli(0, beta * sqrt(1-(2*x/n).^2)) ## k(x) = -------------------------------------, n/2 <= x <= n/2 ## besseli(0, beta) ## ## See also: kaiserord ## Author: KH <Kurt.Hornik@ci.tuwien.ac.at> ## Description: Coefficients of the Kaiser window ## 2000-02 Paul Kienzle (pkienzle@kienzle.powernet.co.uk) ## use besseli rather than jybess ## note, although Oppenheim & Schafer, 2nd edition has a formula ## which looks completely different than the one herein, it gives ## identical results function w = kaiser (n, beta) if (nargin != 2) usage ("kaiser (n, beta)"); endif if !(is_scalar (n) && (n == round (n)) && (n > 0)) error ("kaiser: n has to be a positive integer"); endif if !(is_scalar (beta) && (beta == real (beta))) error ("kaiser: beta has to be a real scalar"); endif if (n == 1) w = 1; else m = n - 1; k = (0 : m)'; k = 2 * beta / m * sqrt (k .* (m - k)); w = besseli (0, k) / besseli (0, beta); endif endfunction %!demo %! % use demo("kaiserord");