C/D converter Unit 00 4.1 Periodic impulse s(0=∑6t-nT) traim Sampling 1=-o0 单位冲激串 Conversion from impulse train x(0 to discrete-time x(n]=xc(nT) Continuous- sequence time signal impulse train sampling T=T1 x( x,(4)=x(☑）∑δ(t-nT) (冲激串采样) n= 4T-27 2T4工 T =∑x.(nT)ò(t-nT） x(n] n=-00 sampling period x[n]=x(nT) Sampling sequence -2-101234 (采样序列) 44 ( ) n  t nT  =− = −  4.1 Periodic Sampling Continuous￾time signal Unit impulse train ( ) ( ) c n x nT  t nT  =− = −  ( ) ( ) ( ) s c n x t t nT x t   =− = −  [ ] ( ) c x n = x nT impulse train sampling T: t sampling period n 单位冲激串 Sampling sequence (采样序列) (冲激串采样)