例1:已知某因果系统的对如输入信号 f(t)输出为y(t),h(t)? 0<f<2 <t<1 f()={0 t<0t>2 y()={n(01 解:f(t)=l()-l(t-2) 2 2S F(S)= ,R整个S平面都收敛 y(t)=sin tlu(t)=u(t-D)=sin t +sin (t-1)u(t Y(S) 丌(1+e-)( ) ( ), ( )? 1: f t 的输出为y t 求h t 例 已知某因果系统的对如下输入信号  1 0 2 0 0, 2 ( )   =   t t t f t  sin 0 1 0 0, 1 ( )   =   t t t t y t  整 个 平面都收敛 解 R S s e s e s F s f t u t u t x s s , 1 1 ( ) : ( ) ( ) ( 2) −2 −2 − = − = = − − y(t) = sin t[u(t) −u(t −1)] = sin t + sin  (t −1)u(t −1) 2 2 (1 ) ( )   + + = − s e Y s s