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1、MATLAB机考样题：（1）Generateandplotsequence,with.n1=-20:20;x1=2*cos(pi/8*n1);n2=n1-4;x2=2*cos(pi/8*n2);subplot(2,1,1);plot(n1,x1);subplot(212);plot(n2,x2);（2）WriteaMATLABprogramtocomputeandplottheimpulseresponseofacausalfinite-dimensionaldiscrete-timesystemcharacterizedbyadifferenceequationofthefollo
2、wingform:N=input('请输入你要求的点数N=');num=[1.80.34-1.32-0.86];den=[10.30.5-0.72];x=[1zeros(1,N-1)];（单位冲击）y=filter(num,den,x);plot(0:N-1,y);（3）WriteaMATLABprogramtocomputeanddisplaythepolesandzeros,tocomputeanddisplaythesecond-orderfactoredform,andtogeneratethepole-zeroplotofaz-transformthatisaratioof
3、twopolynomialsinz-1.UsingthisprogramtoanalyzethefollowingG(z):num=[8.16.93-23.8210.5];den=[11.520.18-0.1768];sos=tf2sos(num,den)%tf2sos表示为1/z的升幂zplane(num,den)（4）TrytogiveaprogramtoevaluatethefollowingDTFTintherange:%由于用freqz计算频点至少是2个，所以至少输入两个频点w1=input('请输入你要计算的频点w1=');w2=input('请输入你要计算的频点w2='
4、);w=[w1w2];num=[25953];den=[545211];h=freqz(num,den,w)（6）WriteaMATLABprogramtocomputeandplotthemagnituderesponseofacausalLTIdiscrete-timesystemwithatransferfunctiongivenbynum=0.15*[10-1];den=[1-0.50.7];[h,w]=freqz(num,den,512);plot(w/pi,abs(h));（7）ConsiderthefollowingFIRtransferfunction:UsingMA
5、TLABtodetermineitszerolocationsandplotitsmagnitudeandphaseresponse.h=[10.6.49-0.48-0.14-0.120.09];figure(1)zplane(h,1);[H,w]=freqz(h,1,512);figure(2)plot(w/pi,abs(H));figure(3)plot(w/pi,angle(H));（8）Givenasignal,whenusingasamplingfrequencyfT=20KHz,plotthemagnitudeandphasespectrumofthesampledseq
6、uence(givenlength-64).fs=2e4;n=0:63;x=4*n/fs+cos(0.1*pi*n/fs);h=fft(x,1024);figure(1);plot(0:2/1023:2,abs(h));figure(2);plot(0:2/1023:2,angle(h));（9）designanIIRbutterworthdigitallowpassfilterwiththefollowingspecifications:samplingrateof40kHz,passbandedgefrequencyof4kHz,stopbandedgefrequencyof8k
7、Hz,passbandrippleof0.5dB,andaminimumstopbandattenuationof40dB,plotfrequency-magnitudeandcheckifyourdesignfitsthespecification.fs=40;wp=4*2/fs;%wp<1,没有乘piws=8*2/fs;%ws<1,没有乘piap=0.5;as=40;[n,wn]=buttord(wp,ws,ap,as);[num,den]=butte
