7 Sampling Frequency domain x(1)<>X(jO) plt) K AS a Periodic signa. p()<">P(jo)=∑2mb(0-kO,)=∑0,(0-ko,) k=-00 ()4X2(10)=∑X(m-k)=∑X(o-kO,) 丌7 Sampling     + =− + =− + =− + =− ⎯→ = − = − ⎯→ = − = −  ⎯→ = ⎯→ k s k s s p F p k s s k k s F k F S F X k T x t X j X k p t P j a k k Periodic signal T p t a x t X j ( ) 1 ( ) 2 ( ) ( ) ( ) ( ) 2 ( ) ( ) ( ) 1 ( ) ( ) ( ) . .                  Frequency domain: