ty t zs t zi????)() cos 3()(3)()( 13tettytyty t zs zi??????? 3-8 某 LTI 系统起始状态不变,当输入)(tf =)(t?时,全响应为)(3te t??,当输入)(tf =)(t?时,全响应为)()(tet t????。试求冲激响应)(th 、阶跃响应)(ts 、零输入响应)(ty zi 。解: ??????????)(3)()( )()()()(tetsty tetthty t zi t zi????)(2)()()('tettsts t??????)()()()( )](2)([)()(teteetetettets tttttt????????????????)()()(')(tettsth t??????)(2)()(3)(tetetety ttt zi????????? 3-9 解下列齐次差分方程。(1)0)1(5.0)(???nyny1)1(??y (2)0)1(3)(???nyny1)0(?y (3)0)2(2)1(3)(?????nynyny0)1(??y1)2(??y 解:(1)5.0?? ncny5.0)(?代入1)1(??y 得12?c5.0?c 15.0)( ?? nny (2)3??? ncny)3()(??代入1)0(?y 得1?c nny)3()(??(3)2 1???1 2??? y)1()2()( 21????代入0)1(??y1)2(??y 得:05.0 21???cc125 .0 21??cc 解得4 1??c2 2?c nnny)1(2)2(4)(????? 3-10 解下列差分方程。(1))()2(4)1(5)(nnynyny??????1)1(??y1)2(??y (2))1()2(6)1()(??????nfnynyny0)0(?y1)1(?y)(4)(nnf n??
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