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1、试验一%CreateaRectangularwindowNfft=512;fori=1:3switchi;case1Nwin=10;case2Nwin=30;case3Nwin=100;endw=boxcar(Nwin);[y,f]=freqz(w,1,Nfft);mag=abs(y);holdon;plot(f/pi,20*log10(mag/max(mag)));endxlabel('归一化频率');ylabel('幅度');grid实验二>>%DesignaButterworthDigtia
2、llowpassfilter%Desiredperformentsoftkefilterwp=0.2*pi;ws=0.3*pi;Rp=1.5;Rs=12;Fs=100000;Ts=1/Fs;Nn=128;Wp=(2/Ts)*tan(wp/2);Ws=(2/Ts)*tan(ws/2);%ComputerOderandCutofffrequency[N,Wn]=buttord(Wp,Ws,Rp,Rs,'s')%Computertheanalogfilter[z,p,k]=buttap(N);[Bap,
3、Aap]=zp2tf(z,p,k);[b,a]=lp2lp(Bap,Aap,Wn);%Bilineartransformation%foranalogtodigitalfilterconversion.[bz,az]=bilinear(b,a,Fs)freqz(bz,az,Nn,Fs)title('用Bilinear函数设计数字滤波器')N=4Wn=7.2733e+004Warning:Matrixisclosetosingularorbadlyscaled.Resultsmaybeinaccur
4、ate.RCOND=1.299710e-028.>Inbilinearat89Warning:Matrixisclosetosingularorbadlyscaled.Resultsmaybeinaccurate.RCOND=1.299710e-028.>Inbilinearat90bz=0.00690.02750.04120.02750.0069az=1.0000-2.19222.0439-0.89620.1544实验三%DesignaButterworthDigtiallowpassfilte
5、rwithDesiredperformentsoftkefilterwp=2000*2*pi;ws=3000*2*pi;Rp=3;Rs=15;Fs=10000;Nn=128;%ComputerOderandCutofffrequency[N,Wn]=cheblord(Wp,Ws,Rp,Rs,'s')%Computertheanalogfilter[z,p,k]=buttap(N);[Bap,Aap]=zp2tf(z,p,k);[b,a]=lp2lp(Bap,Aap,Wn);%Impulseinva
6、riancemethod[bz,az]=impinvar(b,a,Fs)freqz(bz,az,Nn,Fs)N=18wn=1.2842e+004Warning:Matrixisclosetosingularorbadlyscaled.Resultsmaybeinaccurate.RCOND=7.489236e-138.>Inbilinearat89InUntitled3at19Warning:Matrixisclosetosingularorbadlyscaled.Resultsmaybeinac
7、curate.RCOND=7.489236e-138.>Inbilinearat90InUntitled3at19bz=1.0e-005*Columns1through140.00000.00010.00050.00280.01050.02950.06380.10940.15050.16720.15050.10940.06380.0295Columns15through190.01050.00280.00050.00010.0000az=1.0e+003*Columns1through140.00
8、10-0.01090.0568-0.18900.4484-0.80471.1309-1.27161.1588-0.86170.5238-0.25950.1040-0.0332Columns15through190.0083-0.00160.0002-0.00000.0000实验四%ChebyshevIlowpassfilter%Desiredperformentswp=20000*pi;ws=30000*pi;Rp=1;Rs=15;%ComputerOrderNebs=sqrt(1
