常用信号的拉氏变换 r() u(ta s + a n+1 δ(t) 6(t-6)6 常用信号的拉氏变换 u(t) S 1 t u t a  ( ) s  a 1 n t 1 ! n s n  (t) 1 ( )0  t t 0 st e 