巴特沃斯带阻数字滤波器设计matlab程序及仿真图.doc

fs=15000;T= 1/fs;rp=1;rs=40;wp1=0.11*pi;wp2=0.81*pi;ws1=0.31*pi;ws2=0.61*pi;%数字带阻滤波器技术指标wc1=(2/T)*tan(wp1/2);%频率预畸变wc2=(2/T)*tan(wp2/2);wr1=(2/T)*tan(ws1/2);wr2=(2/T)*tan(ws2/2);w0=sqrt(wc1*wc2);B=wc2-wc1;wp=1;%归一化通带截止频率ws=wp*(wr1*B) / (w02-wr12) ; %归一化阻带截止频率N,wc=buttord(wp,ws,rp,rs,s)%求滤波器阶数和3dB截止频率 Z,P,K=buttap(N)%设计模拟低通滤波器 Md,Nd=zp2tf(Z,P,K)%将零极点形式转换为传输函数形式M,N=lp2bs(Md,Nd,w0,B)%对低通滤波器进行频率变换，转换为带阻滤波器h,w=freqs(M,N);%模拟带阻滤波器的幅频响应plot(w/(2*pi),abs(h);grid;xlabel(频率Hz);ylabel(幅度);title(模拟带阻滤波器);b,a=bilinear(M,N,15000)%对模拟滤波器双线性变换 figure(1);freqz(b,a);H,W=freqz(b,a); %绘出频率响应；axis(0,1,-100,20);figure(2);plot(W*fs/(2*pi),abs(H);grid on; xlabel(频率/Hz);ylabel(幅值);n=0:199;t=n/fs;x=sin(2*pi*400*t)+3*sin(2*pi*3000*t)+2*sin(2*pi*5000*t);figure(3);subplot(311);plot(t,x);axis(0,0.01,-5,5);title(输入信号);grid on;y=filter(b,a,x);subplot(312);stem(y,.);title(输出序列);grid on;ya=y*sinc(fs*(ones(length(n),1)*t-(n/fs)*ones(1,length(t);subplot(313);plot(t,ya);axis(0,0.01,-3,3);title(输出波形);grid on;t=(0:100)/fs;figure(4)fs=1.5*10000;n=(0:100)/fs;f=sin(2*pi*400*t)+3*sin(2*pi*3000*t)+2*sin(2*pi*5000*t);y=fftfilt(b,x);H1,f1=freqz(f,1);H2,f2=freqz(y,1);f1=f1/pi*fs/2;f2=f2/pi*fs/2;subplot(2,1,1);plot(f1,abs(H1);title(输入信号的频谱);subplot(2,1,2);plot(f2,abs(H2);title(输出信号的频谱);基于Matlab的带阻滤波器设计N = 4wc = 1.7947b = 0.0186 -0.0410 0.1082 -0.1355 0.1810 -0.1355 0.1082 -0.0410 0.018