1N7221 N/2-I X[个之2r]w+w∑2r+G[+WH[k I r=0 r=0 GIo] L 咽 0 x[2]o 1 x[4]o DFT 2 x[61o Gk+o啊 明 X3] 3 0 x[1]o k+斗 X[4] 4 x[3]o, N -point x[55 2 x[5]o DFT bX[6] 6 x[7]o [7] 7 17 Figure 9.4 N-8-point DFT using DIT 17 Figure 9.4   /2 /2 /2 /2 1 1 r 0 r 0 [ ] 2 2[ ]1 N rk N N k r N k X k x W WN r x r W − − = = = +   +     k G k W H k N = + 0 1 2 3 4 5 6 7     2 2 k N N X k G k W H k N +   + = +     N 2 G k G k   + =     N 2 H k H k +  =   0 WN 1 WN 2 WN 3 WN 4 WN 5 WN 6 WN 7 WN ,..., -1 2 N k N = 0,..., -1 2 N k=