Mercurial > forge
view main/comm/inst/@galois/ifft.m @ 9666:67d4cfc5eeb3 octave-forge
comm: update license to GPLv3+
author | carandraug |
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date | Tue, 13 Mar 2012 04:31:21 +0000 |
parents | 90a46621a91d |
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## Copyright (C) 2002 David Bateman ## ## 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 3 of the License, 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 program; if not, see <http://www.gnu.org/licenses/>. ## -*- texinfo -*- ## @deftypefn {Function File} {} ifft (@var{x}) ## ## If @var{x} is a column vector, finds the IFFT over the primitive element ## of the Galois Field of @var{x}. If @var{x} is in the Galois Field ## GF(2^@var{m}), then @var{x} must have @code{2^@var{m} - 1} elements. ## @end deftypefn ## @seealso{ifft} function y = ifft(x) if (nargin != 1) error ("usage: y = ifft (x)"); endif if (!isgalois(x)) error("ifft: argument must be a galois variable"); endif n = 2^x.m - 1; if (n > 255) error ([ "ifft: argument must be in Galois Field GF(2^m), where", ... " m is not greater than 8"]); endif alph = gf(2, x.m, x.prim_poly); [nr,nc] = size(x); if ((nc == 1) && (nr == n)) y = dftmtx(1/alph) * x; elseif ((nc == n) && (nr == 1)) y = (dftmtx(1/alph) * x')'; else error ("ifft: argument must be a vector in GF(2^m) of length 2^m-1"); endif endfunction