i R U(n)/U joL 当Q>0.707UU 1 joC 当Q<0.707 UU 1 0 71172 n √7+02m2-1) U(@、Uc()获最大值（条件是2>1/√2）1 Q 0 K U(K )/U K1 1 K2 UL (Z) ǃUC (Z)㧧ᴰབྷ٬ (ᶑԦᱟ Q ! 1/ 2) x I R jZ L + _ jȦC 1 x U UL /U UC /U ᖃQ>0.707 ᖃQ<0.707 2 2 2 2 1 1 (1 ) Q Q Ș Ș   2 22 2 ( 1) Q Ș 4Ș