N/2仍为偶数,进一步分解:N/2→)N/4 x(n)=x1(m)+x(n+N/4) x4(m)=[x1(n)-x(n+N/4)x2 0.1. 4 A X3(k)=X,(2k)=DFT[x, (n) k=0.1 X4(k)=X1(2k+1)=DF[x4(m) N4N /2仍为偶数，进一步分解：N /2  N /4 3 1 1 4 1 1 / 2 ( ) ( ) ( / 4) ( ) [ ( ) ( / 4)] n N x n x n x n N x n x n x n N W          0,1,..., 1 4 N n   3 1 3 4 1 4 ( ) (2 ) [ ( )] ( ) (2 1) [ ( )] X k X k DFT x n X k X k DFT x n         0,1,..., 1 4 N k  