S(t) +S() AAAAA△AAAA△AAAAA 0 VVVVVV7707770女 +d(a) 四(t) m’（t) m(t) ↑M(w) S (t) S(@) ■频谱： S4M(o)=πA[6(0-oc)+o+oc】+[M(0-oc)+M(o+0c)月[ ( ) ( )] 2 1 ( ) [ ( ) ( )] SA M  = A   −C +  +C + M  −C + M  +C ◼频谱：