K=1;
alpha=2;
sis1=tf(K,[alpha 1]);

den=1; for i=1:4, den=conv(den,[alpha/4 1]); end
sis2=tf(K,den);

den=1; for i=1:16, den=conv(den,[alpha/16 1]); end
sis3=tf(K,den);

den=1; for i=1:64, den=conv(den,[alpha/64 1]); end
sis4=tf(K,den);

step(sis1,sis2,sis3,sis4);
legend('\alpha','\alpha/4','\alpha/16','\alpha/64');
