例:设x1(n)和x2(n)都是N点的实数序列,试用 次N点DFT运算来计算它们各自的DFT DFTIx, (n)]=X,(k) DFTIx,(n)=X,(k) 解:利用两序列构成一个复序列 w(n)=x,(n)+jx, (n W(k)=DFTIw(n]= DFTIX, (n)+jx,(n) DFTL,(n]+jDFT[,(n)] =X1(k)+j2(k) Rely(nI We(k) jImw(n) W(k例：设x1 (n)和x2 (n)都是N点的实数序列，试用 一次N点DFT运算来计算它们各自的DFT: 1 1 DFT x n X k [ ( )] ( ) = 2 2 DFT x n X k [ ( )] ( ) = 解：利用两序列构成一个复序列 1 2 w n x n jx n ( ) ( ) ( ) = + 1 2 W k DFT w n DFT x n jx n ( ) [ ( )] [ ( ) ( )] = = + 则 1 2 = + DFT x n jDFT x n [ ( )] [ ( )] 1 2 = + X k jX k ( ) ( ) Re[ ( )] ( ) w n W k ep Im[ ( )] ( ) op j w n W k