R 986 INSTITUTE OF ARTIFICIAL INTELLIGENCE AND ROBOTICS, XJTU (1)怎样得到X(k) >对x(m)的FT在每个周期内进行N点等间隔点采样: x(m)的傅里叶变换(DTF):X(em)=∑x(n)emn n=-00 2丌 离散化:X(e")24=X(e)=∑ x(n)e ∑ xln)e =X(e)=X(k) n=-00 imz」 >对x(n)的z变换X(z)在单位圆 的N个等间隔点上采样: Re[ z k X(k)=X()=2=(eN 单位圆 7(k=N-1) z平面 数字信号处理简明教程Institute of Artificial Intelligence and Robotics, XJTU 1986 数字信号处理简明教程 2 2 ( ) ( ) ( ) j k N j k N z e X k X z X e    = = = X k( )  （1）怎样得到 x(n)的傅里叶变换（DTFT）： ( ) ( ) jw jwn n X e x n e  − =− =  2 0 ( ) ( ) ( ) ( ) 2 j k N jw jk w k N X k X e X e X e     = 离散化： = = = 0 0 2 ( ) ( ) ( ) ( ) j kn jk jk n N n n X k X e x n e x n e       − − =− =− = = =   2 0 ( ) ( ) ( ) ( ) 2 j k N jw jk w k N X k X e X e X e     = = = = 0 0 2 ( ) ( ) ( ) ( ) j kn jk jk n N n n X k X e x n e x n e       − − =− =− = = =   X k( )  = 0 2 N   = ➢ 对x(n)的FT在每个周期内进行N点等间隔点采样： ➢ 对x(n)的z变换X(z)在单位圆 的N个等间隔点上采样：