X(k)
X(nT), n =0, 1, 2, , N -1 (2.19), (2.20):
, k =0, 1, 2, , N -1; (2.21)
, n=0, 1, 2, , N -1, (2.22)
,
WN N, , m =0, 1, 2, . (2.21) x(nT) k (N -1) (N -1) 4(N -1) (2 N -2) , N k =0, 1, 2, , N -1 N 2 N 2 . , N ( ) , .
, . , N - , (N /2)- , . (N /2)- (N /2)2*2= N 2/2 , .. ( ) 2 . (N /2)- (N /4)- . N =2n, n>0 , , 2- . n=log2 N , N - N n, .. . N =1000 (2.21) N 2=106 , 104, .. .
, , , x(nT) , X(k). N log2 N ( ) , .