4.1 periodic sampling 1. ideal sample x[s]=x(o1-=X(I T:sample period fs-1/T sample rate s=2兀/T: sample rate x(1) x2(D) x s( 2T-T0 2T t 2T-T0 T 2T rIn 101234n 2-1012344.1 periodic sampling 1.ideal sample x[n] x (t)| x (nT) = c t=nT = c T：sample period fs=1/T:sample rate Ωs=2π/T:sample rate