em(t)m(t)sin 2ot 相对2c 缓慢变化 lim 1 ∫3m()m()sin2atot=0 T→>∞T 1 m2()+m2(t)=m2(t) mo(t)=s(t)cost =1m(4) 4 [:m(t)]2 16 17(t7 m t m t t 2 c ( ) ˆ( )sin  = →  = − 2 2 ( ) ˆ( )sin 2 0 lim 1 T T c m t m t tdt T T  相对2ωc 缓慢变化 ˆ ( ) 8 1 ( ) 8 1 2 2 S m t m t i = + ( ) 4 1 2 = m t m t s t t m  c ( ) ( )cos 0 = m t t m t t t  c  c  c [ ( )cos ˆ( )sin ]cos 2 1 = ( ) − 4 1 = m t ( ) 16 1 ( )] 4 1 [ 2 2 0 S = m t = m t