x()=x()∑6(t-n7)=∑x(n7)6(-n7) L[x:()=∑x7)em=X(e) X(2)=∑难n]zn let: zae 1= Laplace transform (> continuous time signal [-relation z-transform discrete-time signal QT z三已 (o+jQ2)T' JO r=ooT relation between s0: O=QT F s and z 数字频率(单位rad)和模拟频率(rad/s)的关系 1212 sT T ( ) j T j T j z e e e e re  +     = = =  = ( ) [ ] n n X z x n z  − =− =  so： T r e  = relation between  = T s z and Laplace transform continuous time signal z-transform discrete-time signal relation [ ] ( ) ( ) ( ) snT sT s n x t x nT e X e  − =− L = =  sT let： z e @ 数字频率(单位rad)和模拟频率(rad/s)的关系 s c c ( ) ( ) ( ) ( ) ( ) n n x t x t t nT x nT t nT     =− =− = − = −  