dft.m

数字信号处理（机械工业出版社）的源码

function [Xk] = dft(xn,N)
% Computes Discrete Fourier Transform
% -----------------------------------
% [Xk] = dft(xn,N)
% Xk = DFT coeff. array over 0 <= k <= N-1
% xn = N-point finite-duration sequence
%  N = Length of DFT
%
n = [0:1:N-1];                       % row vector for n
k = [0:1:N-1];                       % row vecor for k
WN = exp(-j*2*pi/N);                 % Wn factor
nk = n'*k;                           % creates a N by N matrix of nk values
WNnk = WN .^ nk;                     % DFT matrix
Xk = xn * WNnk;                      % row vector for DFT coefficients