I2(s)= s2U1(s)-(2s+1)(s+1)2U1(s) s2+5s+2 s2+3s+1-(2s+1 故,转移导纳Y21(s)为 I2(s)_(s+1)2 Y2(s)=U1(s) 题解14-4图 可求得Y21(s)有二阶零点:x1=z2=-1;2个极点:1 -5+√17 0.43845, 5-√17 p2 =-4.56155。其零点极点图如题解14-4图(b)所示