北邮考研信号与系统专业课试卷及答案2007B

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1、(B)B17236t1.ò-¥(2t-1)dt=_______{7:1*:1*'2..sint69tó)õ9tõ)&dt=0ó582(82(%3.f(t)=u(t)f(t)=u(t+1)-u(t-1)g(t)=f(t)*f(t)=12124.tu(t)-t5.g(t)=(1-e)u(t)26.x(t)y(t)=x(t)7.F[f(t)]=F()F[f(-2t+1)]-at8.f(t)F(s)teft()9.1.1t0vc(0-)=-Es1.21.2AB1sC1.11.216(B)110.Hs()=s+0.5011.f(t)Fs()=(>-aa)22()sa+

2、+093+j12.LTIHj()=286+-j13.et()=+Esin(t)Etsin2()1121rt()=KE1sin(1t-1)+-KEt2sin2(11)14.x(n)=sin(0.3n)-1-2--3415.zXz()1=++2345zz++zz16.xn()=-{323}hn()=-{241}n17.xn()=(--0.82)un()z6481.f1øt÷,f2øt÷2.1føt÷ãf1øt÷f2øt÷fø0÷=f1(t)f2(t)2211tt01234012342.126(B)2.2.2f(t)F()=R()+jX()y(t)ÛY()=?f

3、(t)y(t)2211tt012-4-20242.23.Hø÷2.3føt÷=1õcostyøt÷H()()0F()Y()=0H()2.34.ft()=sin(2)t×-ut(1)s+65.Fs()=(ss++25)()

4、

5、næö16.xn()=ç÷zèø2z117.Xz()=<

6、ïe>0Hj()=íæöïjç÷èø2îe<0ah(t)bxt()=+costtsinx(t)y(t)12584.1m(t)M(j)4.2H(j)x(t)s=3my(t)y(t)H1(j)r(t)1x(t)2y(t)3H1(j)cx(t)r(t)=x(t)c46(B)4.1687Vs()21Hs()=Vs()12Ks2ss++4478y(n)+3y(n-1)+2y(n-2)=x(n)y(-1)=0,ny(-2)=0.5x(n)=(0.5),n0y(n)1091H(z)2h[n]j3He()56(B)4ab0rad/s1rad/s09810r(t)r(t)12

7、(t)L+r2(t)-1R2e(t)1+C+R1r1(t)2(t)e2(t)--1066BB1æ1ö1.uçt-÷2.13.(t+1)u(t+1)-(t-1)u(t-1)2è2ø1-t4.t[-u(-t)+u()t]5.eu(t)6.211æ-ö-j7.Fe28.9.ç÷2è2ø1011121314151617186481fø0÷=2y(j)=F(2)+F(-2)=2R(2)3yøt÷ã3õ2cost4.5.6.7.8.81æö-jT=1=2f()t®F()=Sae411o0ç÷jè4øn1n11ænö-j1ænö-jF(n)=[F()]=S1÷e4=Sae

8、210=naçç÷T1jnè4øj2nè2ø11¥n1ænö-jF()=2åSa÷e2×(-2n)Tç-¥j2nè2ø821B1T2R()=Tlim®¥ò0Ecos0t×cos0(t-)(ut-)dtT>0,f(t)×f(t-)1T+é2221ùR()=limEcost×cos+Esin×sin2tdtT®¥Tòê00020úëû1éT+21+cos20tT+21ù=limEcosdt+Esin×sin2tdtT®¥Têò02ò020úëû21T+21E=limEcosdt=cosò00T®¥T222E[(-0)+(+0)]28888108éR11ùéR1ù

9、é&()tùê--úé()tùê0úée()tù1LL1L1ê&ú=ê11úê()ú+ê1úê()úêë2()túûê-úë2tûê0úëe2tûêëCR2CúûêëR2Cúûér1(t)ùé-R10ùé1(t)ùéR10ùée1(t)ùê()ú=êúê()ú+êúê()úër2tûë01ûë2tûë0-1ûëe2tû22