李洁《数字信号处理》2005③ ATAB用 MATLAB实现DFT function (xk= dft(xn, N) o Computes Discrete Fourier Transform ye xk=dft(xn, N) %e Xk= DFT coeff. array over 0<=k<=N-I Z xn=N-point finite-duration sequence n=[0: 1: N-1 row vector for n [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 DF coefficients 习题开讲 习题1(6) 0<m<N 解(6)X(k)=∑ 。+1S。一m+m Digital Signal Processing _ Jie Li 2005李洁《数字信号处理》2005® Digital Signal Processing__Jie Li 2005® 4 MATLAB 用MATLAB实现DFT 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 1]; % row vecor for k WN = exp( WN = exp(-j*2*pi/N); % j*2*pi/N); % Wn factor nk = n'*k; % creates a N by N matrix of = n'*k; % creates a N by N matrix of nk values WNnk = WN .^ = WN .^ nk; % DFT matrix Xk = xn * WNnk; % row vector for DFT coefficients ; % row vector for DFT coefficients 习题1（6） 解 习题开讲