a=0.25;
w0=4*pi;
alpha=0.96;
tetha=pi/20;
num=[1 a];
den=[1 2*a a^2+w0^2];
Fs=tf(num,den)
T=1;
numd=[1 -alpha*cos(tetha) 0];
dend=[1 -2*alpha*cos(tetha) alpha^2];
Fz=tf(numd,dend,T)
hd=dimpulse(numd,dend);