④求拉民速变换:0(号+2y Ists (6)画S域模型电路:参考P173例4-5-4 a节点(3+n2、s)-U()×2=24+5(s2()=1() 节点:-U() ()=0, +3s+24 (s)=0 a节点:(24+sU(s)-24U(s)=72l,(s) (l)式 b节点:sU()-(4s+24。≥(s)=0 (2)式 由(2)式:U() 4s+24 U() (2 4+s4s+24)-24s 72 4s2+120s+576-24s 92+24+141()=18 H U(s) k 2 1(s)(s+12)s+12 k=(s+12)H(s) 18 n()+1++12)(20604189018120 Pl79(1)1)s2Y(s)=F(s)+4sY(s)-Y(s)s2(s)-4s(s)+Y(s)=F(s) (2-4s+ly(s)=F(s 4±√16-4×1×1 √3;H(s)= k k2 北京邮电大学网络学院罗老师编④求拉氏逆变换得:u( )t e (t) t ⎟ε ⎠ ⎞ ⎜ ⎝ ⎛ = + −6 2 7 2 5 (6)画 S 域模型电路:参考 P173 例 4-5-4 ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) 0 3 3 24 3 1 0; 8 1 1 3 1 3 1 : 3 1 72 24 ; 3 1 3 72 1 : = + + ⎟ = − ⎠ ⎞ ⎜ ⎝ ⎛ − × + + + − = + ⎟ − × = ⎠ ⎞ ⎜ ⎝ ⎛ + U s s s s U s U s s b U s U s U s I s s U s U s Is s s a a o a o a o s a o s 节点 节点 ( ) ( ) ( ) ( ) ( ) 节点 ( ) ( ) ( ) ( )式 节点 式 : 4 24 0 2 : 24 24 72 1 − + ≥ = + − = b sU s s U s a s U s U s I s a o a o s ( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) [ ] ( ) ( ) ( ) ( ) ( ) h( )t ( ) te e ( )t e ( t) (t) s s H s s ds d s H s ds d k k s H s s s k s k I s U s H s I s s s I s s s s I s s s s s U s U s I s s s s s U s s s U s t t t s s s s s o o s s s a o o s ; 216 18 ε 18 1 12 ε 12 18 12 216 12 18 18 12 18 216; ; 12 12 12 18 24 144 18 4 120 576 24 72 72 24 4 24 24 ; 4 24 2 : 12 12 12 2 12 12 2 2 12 12 2 1 2 2 1 2 2 2 = − + = − + + + − ∴ = = + = = = + = = − + + + = = + = + + = + + − = = + + + − = − − − =− =− =− =− 由 式 P179(1)1) s Y( )s = F( )s + 4sY(s)− Y(s); s Y(s)− 4sY(s)+ Y(s) ( = F s 2 2 ) ( ) ( ) ( ) ( ) ( ) ( ) 4 1 1 4 1 ; 2 2 − + − + = = = F s s s Y s s s Y s F s H s ( ) ( )( )( ) 2 3 1 2 3 2 3 1 2 3 2 3 2 3 2 3; 2 4 16 4 1 1 2 3 1 1 2 1,2 = − − − + = − − − + + − − = ± = ± − × × = s= + s s k s s k s k Q P H s ( )( )( ) 2 3 1 2 3 2 3 1 2 3 2 3 2 = − − − − + = − + s= − s s k s 北京邮电大学 网络学院 罗老师编 5