z-Transform Example- The z-transform u(z of the unit step sequence u[n] can be obtained from X(z)= for az <1 1-az by setting a=1 for z<1 ROC is the annular region 1<=<oo Copyright C 2001, S K MitraCopyright © 2001, S. K. Mitra 11 z-Transform • Example - The z-transform (z) of the unit step sequence [n] can be obtained from by setting  = 1: • ROC is the annular region , for 1 1 1 ( ) 1 1   − = − − z z X z 1 z   for 1 1 1 1 1  − = − − z z  (z)