I3- k T=cz-2,T2 bz-,T3 a A1=△2=△3=△=1 H(z)=a+bz+cz-21 2 1 2 3 3 1 2 2 1 ( ) 1 , , 1 ( ) − − − − = + +  =  =  =  = = = =   =  H z a bz cz T cz T bz T a H z T k k k