ex0511.m

数字信号处理（机械工业出版社）的源码

n = [0:1:99]; x = cos(0.48*pi*n)+cos(0.52*pi*n);
% Spectrum based on the first 10 samples of x(n)
n1 = [0:1:9]; y1 = x(1:1:10);
subplot(2,3,1); stem(n1,y1); 
title('x(n), 0 <= n <= 9','fontsize',8);xlabel('n'); axis([0,10,-2.5,2.5]); set(gca,'fontsize',8)
Y1 = fft(y1); magY1 = abs(Y1(1:1:6)); k1 = 0:1:5; w1 = 2*pi/10*k1;
subplot(2,3,4);stem(w1/pi,magY1);title('Samples of DTFT Magnitude','fontsize',8);
xlabel('frequency in pi units'); axis([0,1,0,10]); set(gca,'fontsize',8)

n2= [0:1:99]; y2 = [x(1:1:10) zeros(1,90)];
subplot(2,3,2); stem(n2,y2); title('x(n), 0 <= n <= 9 + 90 zeros','fontsize',8); xlabel('n')
axis([0,100,-2.5,2.5]); set(gca,'fontsize',8)
Y2 = fft(y2);magY2=abs(Y2(1:1:51)); k2 = 0:1:50; w2 = 2*pi/100*k2;
subplot(2,3,5); plot(w2/pi,magY2); title('DTFT Magnitude','fontsize',8); 
xlabel('frequency in pi units'); axis([0,1,0,10]); set(gca,'fontsize',8)

subplot(2,3,3); stem(n,x); title('x(n), 0 <= n <= 99','fontsize',8);xlabel('n')
axis([0,100,-2.5,2.5]); set(gca,'fontsize',8)
X = fft(x); magX=abs(X(1:1:51)); k = 0:1:50; w = 2*pi/100*k;
subplot(2,3,6);plot(w/pi,magX);title('DTFT Magnitude','fontsize',8);
xlabel('frequency in pi units'); axis([0,1,0,60]); set(gca,'fontsize',8)