iir滤波器matlab源程序

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1、IIR滤波器matlab源程序（1）IIR一阶低通滤波器clear;fi=1;fs=10;Gc2=0.9;wc=2*pi*fi/fs;     omegac=tan(wc/2);alpha=(sqrt(Gc2)/sqrt(1-Gc2))*omegac;a=(1-alpha)/(1+alpha);b=(1-a)/2;w=0:pi/300:pi;     Hw2=alpha^2./(alpha^2+(tan(w/2)).^2);plot(w/pi,Hw2);grid;holdon; （2）一阶高通滤波器clear;fi=1;fs

2、=10;Gc2=0.5;wc=2*pi*fi/fs;omegac=tan(wc/2);alpha=(sqrt(1-Gc2)/(sqrt(Gc2)))*omegac;14a=(1-alpha)/(1+alpha);b=(1+a)/2;w=0:pi/300:pi;Hw2=(tan(w/2).^2)./(alpha^2+(tan(w/2)).^2);plot(w/pi,Hw2);grid;holdon;（3）Notch嵌波滤波器clear;Gb2=0.5;w0=0.35*pi;deltaw=0.1*pi;b=1/(1+tan(de

3、ltaw/2)*(sqrt(1-Gb2)/sqrt(Gb2)));B=[1-2*cos(w0)1].*b;A=[1-2*b*cos(w0)(2*b-1)];w=0:pi/500:pi;H=freqz(B,A,w);plot(w/pi,abs(H));grid; （4）Peak滤波器clear;14Ac=3;Gb2=10^(-Ac/10);w0=0.35*pi;deltaw=0.1*pi;b=1/(1+tan(deltaw/2)*(sqrt(Gb2)/sqrt(1-Gb2)));B=[10-1].*(1-b);A=[1-2*b

4、*cos(w0)(2*b-1)];w=0:pi/500:pi;H=freqz(B,A,w);plot(w/pi,abs(H));grid; （5）IIR低通滤波（Butterworth）%IIRLowpassUseButterworthclear;fs=20;fpass=4;fstop=5;Ap=0.5;As=10;wp=2*pi*fpass/fs;ws=2*pi*fstop/fs;omegap=tan(wp/2);omegas=tan(ws/2);ep=sqrt(10^(Ap/10)-1);es=sqrt(10^(As/1

5、0)-1);14N=ceil(log(es/ep)/log(omegas/omegap));omega0=omegap/ep^(1/N);K=floor(N/2);fori=1:K   theta(i)=pi*(N-1+2*i)/(2*N);endfori=1:K   G(i)=omega0^2/(1-2*omega0*cos(theta(i))+omega0^2);endfori=1:K   a1(i)=2*(omega0^2-1)/(1-2*omega0*cos(theta(i))+omega0^2);endfori=1

6、:K   a2(i)=(1+2*omega0*cos(theta(i))+omega0^2)/(1-2*omega0*cos(theta(i))+omega0^2);endifK<(N/2)   G0=omega0/(omega0+1);a0=(omega0-1)/(omega0+1);endw=0:pi/300:pi;Hw2=1./(1+(tan(w/2)/omega0).^(2*N));plot(w/pi,Hw2);grid;14（6）IIR高通滤波（Butterworth）%IIRHightpassUseButterw

7、orthclear;fs=20;fpass=5;fstop=4;Ap=0.5;As=10;wp=2*pi*fpass/fs;ws=2*pi*fstop/fs;omegap=cot(wp/2);omegas=cot(ws/2);ep=sqrt(10^(Ap/10)-1);es=sqrt(10^(As/10)-1);N=ceil(log(es/ep)/log(omegas/omegap));omega0=omegap/ep^(1/N);K=floor(N/2);fori=1:K   theta(i)=pi*(N-1+2*i)/(

8、2*N);endfori=1:K   G(i)=omega0^2/(1-2*omega0*cos(theta(i))+omega0^2);endfori=1:K   a1(i)=-2*(omega0^2-1)/(1-2*omega0*cos(theta(i))+omega0^2);end1