常见滤波器Matalab程序

%写上标题%设计低通滤波器：[N,Wc]=buttord()%估算得到Butterworth低通滤波器的最小阶数N和3dB截止频率Wc[a,b]=butter(N,Wc); %设计Butterworth低通滤波器[h,f]=freqz(); %求数字低通滤波器的频率响应figure(2); % 打开窗口2subplot(221); %图形显示分割窗口plot(f,abs(h)); %绘制Butterworth低通滤波器的幅频响应图title(巴氏低通滤波器'');grid; %绘制带网格的图像sf=filter(a,b,s); %叠加函数S经过低通滤波器以后的新函数subplot(222);plot(t,sf); %绘制叠加函数S经过低通滤波器以后的时域图形xlabel('时间(seconds)');ylabel('时间按幅度');SF=fft(sf,256); %对叠加函数S经过低通滤波器以后的新函数进行256点的基—2快速傅立叶变换w= %新信号角频率subplot(223);plot()); %绘制叠加函数S经过低通滤波器以后的频谱图title('低通滤波后的频谱图');%设计高通滤波器[N,Wc]=buttord()%估算得到Butterworth高通滤波器的最小阶数N和3dB截止频率Wc[a,b]=butter(N,Wc,'high'); %设计Butterworth高通滤波器[h,f]=freqz(); %求数字高通滤波器的频率响应figure(3);subplot(221);plot(f,abs(h)); %绘制Butterworth高通滤波器的幅频响应图title('巴氏高通滤波器');grid; %绘制带网格的图像sf=filter(); %叠加函数S经过高通滤波器以后的新函数subplot(222);plot(t,sf); ;%绘制叠加函数S经过高通滤波器以后的时域图形xlabel('Time(seconds)');ylabel('Time waveform');w; %新信号角频率subplot(223);plot()); %绘制叠加函数S经过高通滤波器以后的频谱图title('高通滤波后的频谱图');%设计带通滤波器[N,Wc]=buttord([)%估算得到Butterworth带通滤波器的最小阶数N和3dB截止频率Wc[a,b]=butter(N,Wc); %设计Butterworth带通滤波器[h,f]=freqz(); %求数字带通滤波器的频率响应figure(4);subplot(221);plot(f,abs(h)); %绘制Butterworth带通滤波器的幅频响应图title('butter bandpass filter');grid; %绘制带网格的图像sf=filter(a,b,s); %叠加函数S经过带通滤波器以后的新函数subplot(222);plot(t,sf); %绘制叠加函数S经过带通滤波器以后的时域图形xlabel('Time(seconds)');ylabel('Time waveform');SF=fft(); %对叠加函数S经过带通滤波器以后的新函数进行256点的基—2快速傅立叶变换w=( %新信号角频率subplot(223);plot(')); %绘制叠加函数S经过带通滤波器以后的频谱图title('带通滤波后的频谱图');实例应用：matlab设计的带通滤波器方法改变参数就行了cheb1% wp1=0.45*pi;wp2=0.65*pi;ws1=0.3*pi;ws2=0.75*pi;Rp=1;Rs=40% =============双线型变换法=========================================wp1=0.45*pi; wp2=0.65*pi;ws1=0.3*pi; ws2=0.75*pi;Rp=1; Rs=40;Wp1=tan(wp1/2); Wp2=tan(wp2/2);Ws1=tan(ws1/2); Ws2=tan(ws2/2);BW=Wp2-Wp1; W0=Wp1*Wp2; W00=sqrt(W0);WP=1; WS=WP*(W0^2-Ws1^2)/(Ws1*BW);[N,Wn]=cheb1ord(WP,WS,Rp,Rs,'s');[B,A]=cheby1(N,Rp,Wn,'s');[BT,A T]=lp2bp(B,A,W00,BW);[num,den]=bilinear(BT,A T,0.5);[h,omega]=freqz(num,den,64);subplot(2,2,1);stem(omega/pi,abs(h));xlabel('\omega/\pi');ylabel('|H(z)|');subplot(2,2,2);stem(omega/pi,20*log10(abs(h)));xlabel('\omega/\pi');ylabel('增益.dB');%=============双线性变化法2=================================ws=0.6*pi;Ap=1;As=25;wp=0.4*pi;T=0.001;Fs=1/T;wp=wp/T;ws=ws/T;N=buttord(wp,ws,Ap,As,'s');fprintf('\nN=%d\n',N);wc=wp/((10^(0.1*Ap)-1)^(1/2/N));fprintf('\nwc=%.4e\n',wc);[numa,dena]=butter(N,wc,'s');fprintf('\n');disp('A numerator polynomial');fprintf('%.4e\n',numa);fprintf('\n');disp('A Denominator polynomial');fprintf('%.4e\n',dena);[numd,dend]=bilinear(numa,dena,Fs);w=linspace(0,pi,512);h=freqz(numd,dend,w);norm=max(abs(h));numd1=abs(h)/norm;plot(w/pi,20*log10(numd1));grid;%xlable('Normalized frequency');%ylable('Gain,dB');fprintf('\n');disp('D numerator polynomial');fprintf('%.4e\n',numd);fprintf('\n');disp('D numerator polynomial');fprintf('%.4e\n',dend);% =============直接法================================= wp1=0.45*pi; wp2=0.65*pi;ws1=0.3*pi; ws2=0.75*pi;Rp=1; Rs=40;Wp=[wp1/pi,wp2/pi]; Ws=[ws1/pi,ws2/pi];[N,Wn]=cheb1ord(Wp,Ws,Rp,Rs);[B,A]=cheby1(N,Rp,Wn);[h,omega]=freqz(B,A,64);subplot(2,2,3);stem(omega/pi,abs(h));xlabel('\omega/\pi');ylabel('|H(z)|');subplot(2,2,4);stem(omega/pi,20*log10(abs(h)));xlabel('\omega/\pi');ylabel('增益.dB');%cheby2%% wp1=0.45*pi;wp2=0.65*pi;ws1=0.3*pi;ws2=0.75*pi;Rp=1;Rs=40% =============脉冲响应不变法的程序================================= wp=0.4*pi;ws=0.6*pi;Ap=1;As=25;wp=0.4*pi;T=0.001;Fs=1/T;wp=wp/T;ws=ws/T;N=buttord(wp,ws,Ap,As,'s');fprintf('\nN=%d\n',N);wc=wp/((10^(0.1*Ap)-1)^(1/2/N));fprintf('\nwc=%.4e\n',wc);[numa,dena]=butter(N,wc,'s');fprintf('\n');disp('A numerator polynomial');fprintf('%.4e\n',numa);fprintf('\n');disp('A Denominator polynomial');fprintf('%.4e\n',dena);[numd,dend]=impinvar(numa,dena,Fs);w=linspace(0,pi,512);h=freqz(numd,dend,w);norm=max(abs(h));numd1=abs(h)/norm;plot(w/pi,-20*log10(numd1));grid;%xlable('Normalized frequency');%ylable('Gain,dB');fprintf('\n');disp('D numerator polynomial');fprintf('%.4e\n',numd);fprintf('\n');disp('D numerator polynomial');fprintf('%.4e\n',dend);各种滤波器形式的MATLAB参考程序和仿真内容%*******************************************************************%%mode: 1--巴特沃斯低通；2--巴特沃斯高通；3--巴特沃斯带通；4--巴特沃斯带阻% 5--契比雪夫低通；6--契比雪夫高通；7--契比雪夫带通；8--契比雪夫带阻%fp1,fp2：通带截止频率，当高通或低通时只有fp1有效%fs1, fs2：阻带截止频率，当高通或低通时只有fs1有效%rp: 通带波纹系数%as: 阻带衰减系数%sample: 采样率%h: 返回设计好的滤波器系数%*******************************************************************% function[b,a]=iirfilt(mode,fp1,fp2,fs1,fs2,rp,as,sample)wp1=2*fp1/sample;wp2=2*fp2/sample;ws1=2*fs1/sample;ws2=2*fs2/sample;%得到巴特沃斯滤波器的最小阶数N和3bd频率wnif mode<3[N,wn]=buttord(wp1,ws1,rp,as);elseif mode<5[N,wn]=buttord([wp1 wp2],[ws1 ws2],rp,as);%得到契比雪夫滤波器的最小阶数N和3bd频率wnelseif mode<7[N,wn]=cheb1ord(wp1,ws1,rp,as);else[N,wn]=cheblord([wp1 wp2],[ws1 ws2],rp,as);end%得到滤波器系数的分子b和分母aif mode= =1[b，a]=butter(N,wn);endif mode= =2[b，a]=butter(N,wn,/high/);endif mode= =3[b，a]=butter(N,wn);endif mode= =4[b，a]=butter(N,wn,/stop/);endif mode= =5[b，a]=cheby1(N,rp,wn);endif mode= =6[b，a]=cheby1(N,rp,wn,/high/);endif mode= =7[b，a]=cheby1(N,rp,wn);endif mode= =8[b，a]=cheby1(N,rp,wn,/stop/);endset(gcf,/menubar/,menubar);freq_response=freqz(b,a);magnitude=20*log10(abs(freq_response));m=0:511;f=m*sample/(2*511);subplot(3,1,1);plot(f,magnitude);grid; %幅频特性axis([0 sample/2 1.1*min(magnitude) 1.1*max(magnitude)]); ylabel('Magnitude');xlabel('Frequency-->');phase=angle(freq_response);subplot(3,1,2);plot(f,phase);grid; %相频特性axis([0 sample/2 1.1*min(phase) 1.1*max(phase)]);ylabel('Phase');xlabel('Frequency-->');h=impz(b,a,32); %32点的单位函数响应t=1:32;subplot(3,1,3);stem(t,h);grid;axis([0 32 1.2*min(h) 1.1*max(h)]);ylabel('h(n)');xlabel('n-->');。