gusucode.com > 信号处理工具箱 - signal源码程序 > signal\signal\signal\dftmtx.m
function b = dftmtx(n) %DFTMTX Discrete Fourier transform matrix. % DFTMTX(N) is the N-by-N complex matrix of values around % the unit-circle whose inner product with a column vector % of length N yields the discrete Fourier transform of the % vector. DFTMTX(LENGTH(X))*X is the same as FFT(X). % % The inverse discrete Fourier transform matrix is % CONJ(DFTMTX(N))/N. See also FFT and IFFT. % Author(s): C. Denham, 7-21-88 % Copyright (c) 1988-98 by The MathWorks, Inc. % $Revision: 1.1 $ $Date: 1998/06/03 14:42:25 $ f = 2*pi/n; % Angular increment. w = (0:f:2*pi-f/2).' * i; % Column. x = 0:n-1; % Row. b = exp(-w*x); % Exponentiation of outer product.