信号与系统第一二章答案.doc 16页

'Chapter22.1Solution:Becausex[n]=(120–1),h[n]=(202),then(a).So,(b).accordingtothepropertyofconvolutioin:(c).2.3Solution:thefigureofthey[n]is:2.5Solution:Wehaveknown:,,() Then,,So,y[4]=5,thenAndy[14]=0,then2.7Solution:（a）,(b),(c)SisnotLTIsystem..(d),2.8Solution: Then,Thatis,2.10Solution:(a).Weknow:Then,thatis, So,(b).Fromthefigureof,onlyif,wouldcontainmerelytherediscontinuities.2.11Solution:(a).(b).(c).It’sobviousthat.2.12SolutionConsideringfor,wecanobtain.(Becausemustbenegetive,for). 2.19Solution:(a).Wehaveknown:(1)(2)from(1),from(2),then,but,(b).from(a),weknow 2.20(a).1(b).0hasvalueonlyon,but=0(c).02.23Solution: 2.27Solution,,.2.40Solution(a),Let,then.So,(b)2.46SolutionBecause.FromLTIproperty,weknow whereistheimpulseresponseofthesystem.So,followingequationcanbederived.Finally,2.47SoliutionAccordingtothepropertyofthelineartime-invariantsystem:(a).(b).(c).(d).Theconditionisnotenough.(e).(f).Extraproblems:1.Soluteh(t),h[n](1).(2). Solution:(1).Becauseso(2).BecausesoChapter1Answers1.6(a).NoBecausewhent<0,=0.(b).NoBecauseonlyifn=0,hasvaluable.(c).YesBecauseN=4.1.9(a).T=/5Because=10,T=2/10=/5.(b).Notperiodic.Because,whileisnotperiodic,isnotperiodic.(c).N=2Because=7,N=(2/)*m,andm=7.(d).N=10 Because,thatis=3/5,N=(2/)*m,andm=3.(e).Notperiodic.Because=3/5,N=(2/)*m=10m/3,it’snotarationalnumber.1.14A1=3,t1=0,A2=-3,t2=1or-1Solution:x(t)isisBecause,=3g(t)-3g(t-1)or=3g(t)-3g(t+1)1.15.(a).y[n]=2x[n-2]+5x[n-3]+2x[n-4]Solution:Then,(b).No.Forit’slinearity.therelationshipbetweenandisthesamein-outrelationshipwith(a).youcanhaveatry.1.16.(a).No.Forexample,whenn=0,y[0]=x[0]x[-2].Sothesystemismemory.(b).y[n]=0.Whentheinputis,then,,soy[n]=0. (c).No.Forexample,whenx[n]=0,y[n]=0;whenx[n]=,y[n]=0.Sothesystemisnotinvertible.1.17.(a).No.Forexample,.Soit’snotcausal.(b).Yes.Because:,1.21.Solution:Wehaveknown:(a).(b).(c).(d).1.22. Solution:Wehaveknown:(a).(b).(e).(g)1.23.Solution:Forthen,(a). (b).(c).1.24.Solution:For:then,(a).(b). (c). 1.25.(a).Periodic.T=/2.Solution:T=2/4=/2.(b).Periodic.T=2.Solution:T=2/=2.(d).Periodic.T=0.5.Solution:So,T=2/4=0.51.26.(a).Periodic.N=7Solution:N==7,m=3.(b).Aperriodic.Solution:N=,it’snotrationalnumber.(e).Periodic.N=16Solutionasfollow:inthisequation,,it’speriodisN=2*m/(/4)=8,m=1.,it’speriodisN=2*m/(/8)=16,m=1.,it’speriodisN=2*m/(/2)=4,m=1.So,thefundamentalperiodofisN=(8,16,4)=16.1.31.SolutionBecause.AccordingtoLTIproperty, Extraproblems:1.SupposeSketch.Solution:2.SupposeSketch:(1).(2).Solution:(1).(2).'