例3: (4)x(n)= 双边序列 X(z)=∑ ∑ n三-00 n=0 +1(-3)2-)3(1-32)(1-1z- 3 <|z<3 Rell11 例3: n x n 3 1 (4) ( ) 双边序列 (1 3 )(1 ) 1 3 8 ( 3)( ) 3 3 1 3 1 3 1 ( ) 1 3 1 1 3 1 3 8 1 0 1 z z z z z z z z z X z z z n n n n n j Im[z] 3 3 1 z Re[z] o