机械工程测试技术基础 第三版 课后习题答案(中南适用)

y(t)?0.5?0.816cos(10t?26.56?)?0.2?0.408cos(100t?45??78.69?)?0.408cos(10t?26.56?)?0.0816cos(100t?33.69?)

5.1 h(t)???e??t;(t?0,??0) ?0;(t?0) R????x(?)???h(t)?h(t??)dt??0e??te??(t??)?dt ? ?????????0ee?2?tdt?e2?

5.2 x(t)?A1sin(?1t??1??2)?A2sin(?2t??2??2)

由同频相关，不同频不相关得：

RA21A22x(?)?2cos?1??2cos?2?

5.3：由图可写出方波的基波为x41(t)??sin(?t??2)

Rxy(?)?2?cos(????2)

5.4: Sxy(f)?H(f)Sx(f)

H(f)?Sxy(f)/Sx(f)

Sxy(f)?F[Rxy(?)]

Sx(f)?F[Rx(?)]?F[Rxy(??T)]?F[Rxy(?)]ej?T H(f)?e?j?T

5.5:见图5-16

5.6:由自相关函数的性质可知:

?2x?Rx(0)?Acos0?A x??2rmsx?A

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5.7:由对称性性质:

F{sinc2(t)}?1 f???2?2?f??2

???sinc2(t)dt??2??df??

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