基于MATLAB的数字滤波器的设计程序

1、.IIR 低通滤波器的设计程序为：Ft=8000;Fp=1000;Fs=1200;As=100 ;Ap=1;wp=2*pi*Fp/Ft;ws=2*pi*Fs/Ft;fp=2*Fp*tan(wp/2);fs=2*Fs*tan(ws/2);n11,wn11=buttord(wp,ws,1,50,s);b11,a11=butter(n11,wn11,s);num11,den11=bilinear(b11,a11,0.5);h,w=freqz(num11,den11);axes(handles.axes1);plot(w*8000*0.5/pi,abs(h);xlabel(Frequency/Hz);

2、ylabel(Magnitude);title(巴特沃斯数字低通滤波器);巴特沃斯带通滤波器设计程序为:Ft=8000;Fp1=1200;Fp2=3000;Fs1=1000;Fs2=3200;As=100;Ap=1;wp1=tan(pi*Fp1/Ft);wp2=tan(pi*Fp2/Ft);ws1=tan(pi*Fs1/Ft);ws2=tan(pi*Fs2/Ft);w=wp1*wp2/ws2;bw=wp2-wp1;wp=1;ws=(wp1*wp2-w.2)/(bw*w);n12,wn12=buttord(wp,ws,1,50,s);b12,a12=butter(n12,wn12,s);num2

3、,den2=lp2bp(b12,a12,sqrt(wp1*wp2),bw);num12,den12=bilinear(num2,den2,0.5);h,w=freqz(num12,den12);plot(w*8000*0.5/pi,abs(h);axis(0 4000 0 1.5);xlabel(Frequency/Hz);ylabel(Magnitude);title(巴特沃斯数字带通滤波器);IIR 高通滤波器的设计程序为：Ft=8000;Fp=4000;Fs=3500;wp1=tan(pi*Fp/Ft);ws1=tan(pi*Fs/Ft);wp=1;ws=wp1*wp/ws1;n13,w

4、n13=cheb1ord(wp,ws,1,50,s);b13,a13=cheby1(n13,1,wn13,s);num,den=lp2hp(b13,a13,wn13);num13,den13=bilinear(num,den,0.5);h,w=freqz(num13,den13);axes(handles.axes1);plot(w*21000*0.5/pi,abs(h);xlabel(Frequency/Hz);ylabel(Magnitude);title(切比雪夫型数字高通滤波器);合成信号频谱程序如下：f1=20;f2=200;f3=500;t=(1:100)/2000;x1=sin(2*pi*t*f1);x2=sin(2*pi*t*f2);x3=sin(2*pi*t*f3);x=sin(2*pi*t*f1)+sin(2*pi*t*f2)+sin(2*pi*t*f3);n=1:100;t=n/2000X=fft(x,512);w=(0:255)/256*1000;x=sin(2*pi*t*f1)+sin(2*pi*t*f2)+sin(2*pi*t*f3);axes(handles.axes1);plot(x);xlabel(t);ylabel(幅度);title(合成信号波形图);axes(ha