9.2 decimation-in-time FFT Algorithms r=0 -G(》]+[]。 k-N ,N-1 >k=0,1.,N-1 Xk+ck++]=G网+H个 Nm-eǎnN四-e杨-袋 G+今G内，4+于个 G[k]and H[k]are the N/2-point DFTs ofeach subsequence: g[n]=x[2n]andh[n]=x[2n+1] n=01,-1，k=0116 9.2 decimation-in-time FFT Algorithms   N  , k = + G W k H k   /2 /2 / 2 1 1 r 0 r 0 / 2 [2 ] [2 1] N rk N N N k kr X x r W W W k N x r − − = = = + +   / 2 2 ( ) / 2 /2 ( /2) r N k N j r k N N W e  + − + = ,   2 G k N G k  =     +   2 k k N H H  =   + 0,1,..., 1 2 N k= − ,..., -1 2 N k N = 2 2 2 2 k N N X k G k W H N N k     + N + + + = +             2 k N N G k W H k + = + (( )) (( )) 2 2 , k G k H k N N WN = +         /2 2 /2 N rk j rk e N W  − = = ◆G[k] and H[k] are the N/2-pointDFTs of each subsequence: g[n]=x[2n] and h[n]=x[2n+1] k N =0,1,..., -1 g[r] h[r] , 0,1,..., -1 2 N n= , 0,1,.. - . ., 1 2 N k = , k =0,1,...,N-1