x(=)=∑12 收敛域(ROC):R<<R+ 1)有限长序列 X(2)=∑xk2ROC0<|<∞ k=N 0≤k<N-1 例:x[k R 0其 N X(z)=∑zk ∠ >0 k=0k k X z x k z −  =− ( ) =  [ ] 收敛域(ROC): R−< |z|<R+ 1)有限长序列 k N k N X z x k z − = ( ) =  [ ] 2 1 ROC 0 < z <  [ ] 0 1 0 1 [ ] R k k N x k = N      − = 其它 例： 1 1 0 1 1 ( ) − − − − = − − =  = z z X z z N k N k z  0 z变换定义及收敛域