丌n x(n)coS N IX((k-d)+X(k+D)NRk) (x儿=2/(k-)-X(k+),RA) :DF7{[X(k-1)-X(k+1)]R(k) Wx(n)-Wnlx(n)] 2元nl x(n)=x(n)sin N  2 1 ( )cos (( )) (( )) ( ) 2 N N N nl DFT x n X k l X k l R k N                  2 1 ( )sin (( )) (( )) ( ) 2 N N N nl DFT x n X k l X k l R k N j                  1 (( )) (( )) ( ) 2 N N N IDFT X k l X k l R k j          证： 1 ( ) ( ) 2 nl nl WN N x n W x n j        2 2 ( ) 2 j nl j nl N N e e x n j      2 ( )sin nl x n N  