02936446.rar_4 3 2 1_cir

% x = [1,1,1,1]; subplot(1,1,1); % % a) DTFT w = [0:1:500]*2*pi/500; [H] = freqz(x,1,w); magH = abs(H); phaH = angle(H); phaH(126)=-47.5841*pi/180; subplot(2,1,1); plot(w/pi,magH); grid xlabel(''); ylabel('|X|’); title(' DTFT的幅度') subplot(2,1,2); plot(w/pi,phaH/pi*180); grid xlabel('以pi为单位的频率'); ylabel('度'); title('DTFT的相角') %print -deps2 me0506a.eps pause;subplot(1,1,1) % % b) 4-point DFT N = 4; w1 = 2*pi/N; k = 0:N-1; X = dft(x,N); magX = abs(X), phaX = angle(X)*180/pi subplot(2,1,1);plot(w*N/(2*pi),magH,'--'); axis([-0.1,4.1,-1,5]); hold on stem(k,magX); ylabel('|X(k)|'); title('DFT的幅度: N=4');text(4.3,-1,'k') hold off subplot(2,1,2);plot(w*N/(2*pi),phaH*180/pi,'--'); axis([-0.1,4.1,-200,200]); hold on stem(k,phaX); ylabel('度'); title('DFT相角: N=4');text(4.3,-200,'k') %print -deps2 me0506b.eps