Ex.7.1 Specifications for LTI DT system If input is bandlimited and sampling frequency is high enough to avoid aliasing,then overall system behaves as an LTI continuous-time system H.U)-Hr(j-0 (ea),24kπ/T 当满足：Nyquist采样定 理条件时，DT系统频率 2pπ/T 响应等于整个等效的CT If H(j)is given 系统频率响应 CID H(ej) DIC xa(t) x(n] y(n Ya(t) T LTI discrete-time system Impulse Invariance effective hin]=Th (nT) continuous-time specifications are converted 】to discrete time specifications by:o=2T,fH(e/o)）=lHe/号)，d 长π 等效CT系统频率响应=DT系统频率响应，在所有数字频率范围内 13Ex. 7.1 Specifications for LTI DT system 13 ◆If input is bandlimited and sampling frequency is high enough to avoid aliasing, continuous-time specifications are converted to discrete time specifications by:  = T, then overall system behaves as an LTI continuous-time system ( ) ( ) ( )  , 0, j T c eff H e T H j H j T       =  =   ， effective T   = 当满足: Nyquist采样定 理条件时, DT系统频率 响应等于整个等效的CT 系统频率响应 等效CT系统频率响应=DT系统频率响应, 在所有数字频率范围内 LTI discrete-time system If is given H j c ( ) Impulse Invariance [ ] ( ) c h n Th nT = ( ) ( ), eff H H j j T e   =   