(2)并联系统 H(s) Y1(s) H1(S) X(s) Y(s) H2(S) Y2(s) n H(s)=∑H,() i=1（2）并联系统 H1 (s) H2 (s) X(s) Y1 (s) Y(s) H(s) Y2 (s) ∑H i H (s) = (s) n i =1