3.离散傅里叶级数(DFS) 、DFS变换的推导 由(36)式,X(e)=∑x(m)em 1=-0 △ X(e0)=X(eo+x)∴令(e0)=X(e) 假定x(n)=0,n<0,n>N-1(有限长) X(e)=∑x(m)lm一、DFS变换的推导 ( ) ( ) (+2 ) = j j X e X e ( ) ( ) ~ j j X e X e △ 令 = 假定 x(n) = 0, n 0, n N −1 (有限长) − = − = 1 0 ( ) ( ) ~ N n j j n X e x n e + =− − = n j j n X e x n e 由(3-6)式, ( ) ( ) 3.离散傅里叶级数(DFS)