S 7.2 Selection of Filter Type The transfer function H(z)meeting the frequency response specifications should be a causal transfer function For IIR digital filter design,the IIR transfer function is a real rational function of z1: H(z)= +p2+p222+…+pM2M d4+dz+d2z2+…+dwzw H(z)must be a stable transfer function and must be of lowest order N for reduced computational complexity§7.2 Selection of Filter Type • The transfer function H(z) meeting the frequency response specifications should be a causal transfer function • For IIR digital filter design, the IIR transfer function is a real rational function of z-1: N N M M d d z d z d z p p z p z p z H z − − − − − − + + + + + + + + =   2 2 1 0 1 2 2 1 0 1 ( ) • H(z) must be a stable transfer function and must be of lowest order N for reduced computational complexity