p2
Y(jw)=j[g4(w+4)-g4(w-4)]
4p
=g4(w)*jp[d(w+4)-d(w-4)]
4 p1
=2pg4(w)*jp[d(w+4)-d(w-4)]
42p
p
\ y(t)=4sa(2t)gsin4t=psa(2t)gsin4t
4
3.50 如习题图3-29所示系统，已知f(t)=
sin2t
，H(jw)=jsgn(w)，求输出y(t)。
pt
y(t)=f(t)gcos4t+f(t)*F-1[H(jw)]gsin4tY(jw)11F(jw)*p[d(w+4)+d(w-4)]+[F(jw)gH(jw)]*jp[d(w+4)-d(w-4)]2p2p
=Y1(jw)+Y2(jw)
sin2t2f(t)==sa(2t)« g4(w)
ptp
1Y(jw)=(g4(w+4)+g4(w-4))的图形为： 即1
2