%例程3-12 求解單位沖擊響應(yīng)的幅頻

 N=20;
 a=[0.4 0.3 -1];
 b=[1 -0.2 0.6 0.3];
 x=[1 zeros(1,N-1)];
 k=0:N-1;
 y=filter(a,b,x);
 Fs=1000;
 w=0:pi/Fs:pi;
 h=freqz(a,b,w);
 subplot(2,1,1);
 stem(k,y);
 subplot(2,1,2);
 plot(w/pi,abs(h));