Review periodic sampling T: sampling period(单位s); s()=∑(-m7)6=1: sampling rate(Hz模拟频率 2s=2π/: sampling rate模拟角频率 x(t)=x2(t)(t) rad/s x:()∑6(-n)=∑x(n)5(-m7) 1=-00 xn]=x(tlenr=x( nt x() x() xI n 2T-T0T 2T 4-3-2-01234n8 periodic sampling [ ] ( ) | ( ) c t nT c x n x t x nT = = = T: sampling period (单位s); fs=1/T: sampling rate(Hz); Ωs=2π/T: sampling rate ( )  ( )  =− = − n s t  t nT x t x t s t s c ( ) = ( ) ( ) Review ( ) ( )  =− = −  c n ( )  ( ) x nT t nT  =− = − c  n x t t nT t n 模拟频率 模拟角频率 (rad/s) x t s ( ) x n[ ]