1、n=0:N-1;for k=0:M-1wk(k+1)=2*pi/M*k;X(k+1)=sum(x.*exp(-j*wk(k+1)*n);endclc;clear all;A=444.128;a=50*sqrt(2)*pi;w0=50*sqrt(2)*pi;fs=input(输入采样频率fs=T=1/fs;N=50;xa=A*exp(-a*n*T).*sin(w0*n*T);stem(n,xa,.grid;M=100;Xa,wk=DFT(xa,M);f=wk*fs/(2*pi);plot(f,abs(Xa);1000hz500hz200hzDFT程序:Clcclear allxbn=1,0,0,
2、0;hbn=1,2.5,2.5,1N=4;Xb=fft(xbn,N);Xh=fft(hbn,N);ybn=conv(xbn,hbn);subplot(3,2,1);stem(n,xbn,title(xbn wavesubplot(3,2,2);stem(n,abs(Xb),Xb wavesubplot(3,2,3);stem(n,hbn,hbn wavesubplot(3,2,4);stem(n,abs(Xh),Xh waven1=0:6;Xy=fft(ybn,8);subplot(3,2,5);stem(n1,ybn,ybn wave)n2=0:7;subplot(3,2,6);stem(n
3、2,abs(Xy),Xy wave结果:hbn = 1.0000 2.5000 2.5000 1.0000实验三:第一个方程:a1=1 ,0.75,0.125;b1=1,-1;20;x1=1 zeros(1,20);subplot(2,3,1);y1filter=filter(b1,a1,x1);stem(n,y1filter);y lfilterx1=1 zeros(1,10);h=impz(b1 ,a1,10);subplot(2,3,2);y1conv=conv(h,x1);19;stem(n,y1conv,filledsubplot(2,3,3);impz(b1 ,a1,21);x2=
4、ones(1,21);subplot(2,3,4);y1filter=filter(b1,a1,x2);y1filter_steph=impz(b1,a1,20);y1=conv(h,x2);y1conv=y1(1:21);subplot(2,3,5);stem(n1,y1conv,y1convny1nsubplot(2,3,6);b1=1;impz(b1,a1);第二个方程:a1=1;b1=0.25,0.25,0.25,0.25; x1=1 zeros( 1,20);y 1filterh=impz(b1,a1,10);impz(b1,a1,21);a1=1;b1=0,0.25,0.5,0.7
5、5,ones(1,17);第一个方程结果第二个方程结果:实验四:程序:num=0.0528 0.0797 0.1295 0.1295 0.797 0.0528;den=1 -1.8107 2.4947 -1.8801 0.9537 -0.2336;z,p,k=tf2zp(num,den);m=abs(p);disp(零点disp(z);极点disp(p);增益系数disp(k);sos=zp2sos(z,p,k);figure(1)zplane(num,den)k=256;w=0:pi/k:pi;h=freqz(num,den,w);plot(w/pi,real(h);grid实部omega/
6、pi幅度plot(w/pi,imag(h);虚部Amplitudeplot(w/pi,abs(h);幅度谱幅值plot(w/pi,angle(h);相位谱弧度figure(2)freqz(num,den,128);零点 -1.5870 + 1.4470i -1.5870 - 1.4470i 0.8657 + 1.5779i 0.8657 - 1.5779i -0.0669 + 0.0000i极点 0.2788 + 0.8973i 0.2788 - 0.8973i 0.3811 + 0.6274i 0.3811 - 0.6274i 0.4910 + 0.0000i增益系数 0.0528实验五:w
7、p=input(通带内频率wp=ap=input(容许幅度误差ap=ws=input(频率ws=as=input(阻带衰减as=fs=1;N,Wn=buttord(wp,ws,ap,as,sZ,P,K=buttap(N);Bap,Aap=zp2tf(Z,P,K);b,a=lp2lp(Bap,Aap,Wn);bz,az=bilinear(b,a,fs);H,W=freqz(bz,az,64);subplot(2,1,1);stem(W/pi,abs(H);频率subplot(2,1,2);stem(W/pi,20*log10(abs(H);幅度(dB)bzaz结果:通带内频率wp=0.1*pi容
8、许幅度误差ap=0.5频率ws=0.5*pi阻带衰减as=20bz = 0.0238 0.0714 0.0714 0.0238az =1.0000 -1.6217 1.0505 -0.2384实验六:Blackman方式:b=fir1(21,0.5,blackman(22);y=freqz(b,1);subplot(2,2,1);plot(abs(y);幅度响应subplot(2,2,2);plot(angle(y);相位响应subplot(2,2,3);cj=impz(b,1,20);stem(cj);冲激响应Hamming方式:b=fir1(21,0.5,hamming(22);Hanning方式:b=fir1(21,0.5,hanning(22);cj=i
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