Zero and pole The z-transform is most useful when the infinite sum can be expressed in closed form usually a ratio of polynomials in z(or z-1) P(z Zero: The value of z for which X(=)=0 ◆Poe: The value of z for which X(z)=∞ 2021/1/31 Zhongguo Liu_ Biomedical Engineering_shandong Univ12 2021/1/31 Zhongguo Liu_Biomedical Engineering_Shandong Univ. Zero and pole ( ) ( ) Q(z) P z X z = ◆Zero: The value of z for which X(z) = 0 ◆The z-transform is most useful when the infinite sum can be expressed in closed form, usually a ratio of polynomials in z (or z-1 ). ◆Pole: The value of z for which X(z) = 