巴特沃斯带阻数字滤波器设计matlab程序及仿真图

1、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

2、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=fre

3、qz(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(31

4、2);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=fftfil

5、t(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');Magnitude (dB)0-50-10000.10.20.30.40.50.60.70.8Normalized Frequency ( rad/sample)0.91Phase (degrees)-200-400-600-80000.

6、10.20.30.40.50.60.70.8Normalized Frequency ( rad/sample)0.911.41.210.8幅值0.60.40.2001000200030004000频率/Hz5000600070008000输入信号5-52-200.0010.0020.0030.0040.0050.0060.0070.0080.009输出序列0.01020406080100输出波形1201401601802002-200.0010.0020.0030.0040.0050.0060.0070.0080.0090.01输入信号的频谱200150100500010002000300040005000600070008000输出信号的频谱3020100010002000300040005000600070008000N =4 wc =1.7947 b =0.0186 0.0186 a =1.0000 0.0762 > -0.0