www.gusucode.com > 线性时频分析工具箱 - ltfat-1.0.1源码程序 > 线性时频分析工具箱 - LTFAT\fourier\pchirp.m
function g=pchirp(L,n) %PCHIRP Periodic chirp % Usage: g=pchirp(L,n); % % PCHIRP(L,n) returns a periodic, discrete chirp of length L that revolves % n times around the time-frequency plane in frequency. n must be a whole % number. % % To get a chirp that revolves around the time-frequency plane in time, % use % % dft(pchirp(L,N)); % % The chirp is computed by: % % g(l+1) = exp(pi*i*n*l^2/L) for l=0,...,L-1 % % The chirp has absolute value 1 everywhere. To get a chirp with unit % l^2-norm, divide the chirp by sqrt(L). % % See also: dft, expwave % % References: % H. G. Feichtinger, M. Hazewinkel, N. Kaiblinger, E. Matusiak, and % M. Neuhauser. Metaplectic operators on c^n. To appear, 2006. % % Copyright (C) 2005-2011 Peter L. Soendergaard. % This file is part of LTFAT version 1.0.1 % 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/>. % AUTHOR : Peter Soendergaard % TESTING: OK % REFERENCE: OK error(nargchk(2,2,nargin)); % Compute normalized chirp g=(exp((0:L-1).^2/L*pi*i*n)/sqrt(L)).';