有限长序列的DFT正变换和反变换: X(k)=DF[x(n)=∑x(n)WW0≤k≤N-1 n=0 x(m)=1DFT[X(k)=∑ X(kwWx0≤n≤N-1 N k=0 Et X(k)=2x(n)WR(k)=X(k)R,(k) n=0 (n)=>X(k)WNR(n)=x(n)R,(n) N k=0 其中:WN=e有限长序列的DFT正变换和反变换: 1 0 ( ) [ ( )] ( ) 0 1 N nk N n X k DFT x n x n W k N 1 0 1 ( ) [ ( )] ( ) 0 1 N nk N k x n IDFT X k X k W n N N 2 j N WN e 其中: 1 0 ( ) ( ) ( ) ( ) ( ) N nk N N N n X k x n W R k X k R k 或 1 0 1 ( ) ( ) ( ) ( ) ( ) N nk N N N k x n X k W R n x n R n N