令 x(2r)w k=0.1 (4.207) Blk x(2r+1)W k=01,…,Ny-1 (4208) r=0 则式(4206)可改写为 X(k)=a(k)+Wrb(k) =0.1.…N (4209) 而 A2+k|=4(k)B|+k|=B(k) 因此将式(4.209)完整地写成 X(k)=A(k)+WkB(k k=0.1.2,N x|k+|=4(k)+W2B(k) (4210) 2令 则式(4.206)可改写为 而 因此将式(4.209)完整地写成 ( ) ( ) − = = = − 1 2 2 1 2 2 0,1, N r o r k N A k x r W k N ( ) ( ) − = = + = − 1 2 2 1 2 2 1 0,1, , N r o r k N B k x r W k N (4.207) (4.208) X (k ) = A(k )+W B(k ) k = 0,1, N −1 k N (4.209) ( ) k B(k ) N k A k B N A = = + + 2 2 ( ) ( ) ( ) ( ) ( ) 1 2 0,1,2, 2 2 = − = + + = + + k N A k W B k N X k X k A k W B k N k N k N (4.210)