Q2、序列的移位 k DFS[(n+m)=WN X(k=e X(k) 证:DFS[(n+m)=∑x(n+m)W 0 N-1 令i=n+m x(i) k(i-m Wm∑x()W=形mX(k) i=02、序列的移位 2 [ ( )] ( ) ( ) j mk mk N DF N S x n m W X k e X k         1 0 [ ( )] ( ) N nk N n DFS x n m x n m W   证：      1 ( ) ( ) N m k i m N i m x i W     令i  n  m    1 0 ( ) ( ) N mk ki mk N N N i W x i W W X k         