利用MATLAB实现数字低通滤波器的设计.doc

西 南 石 油 大 学 实 验 报 告 课 程数字信号处理实验项目利用MATLAB实现数字低通滤波器的设计成 绩专业年级通信工程09学 号0907050228指导教师姓 名王延礼同组人姓名实验日期一 实验目的：1学习用Matlab直接设计模拟滤波器和数字滤波器。2学习用冲激响应不变法和双线性变换法的Matlab的实现。 二 实验内容：设计满足下列指标的数字低通滤波器： Wp=0.2*pi, Rp=1db Ws=0.5*pi Rs=20db Fs=1khz1. 利用B、C1型设计出模拟低通滤波器，采用冲激响应不变法、双线性发转换成数字低通滤波器。 2. 直接设计出B、C1型数字低通滤波器。三 实验步骤：程序1Wp=2*pi*0.1*1000;Ws=2*pi*0.25*1000;Rp=1;Rs=20;N,Wn=buttord(Wp,Ws,Rp,Rs,s);z,p,k=buttap(N);B,A=butter(N,Wn,s);freq1=linspace(0,Wp,5);freq2=linspace(Wp,Ws,15);freq3=linspace(Ws,10*pi*2,25);h1=20*log10(abs(freqs(B,A,freq1);h2=20*log10(abs(freqs(B,A,freq2);h3=20*log10(abs(freqs(B,A,freq3);plot(freq1 freq2 freq3/(2*pi),h1,h2,h3);grid;Xlabel(Frequency in Hz);Ylabel(gain in DB);图一程序2wp=0.2*pi;ws=0.5*pi;rp=1;rs=20;fs=1000;omegap=wp*fs;omegas=ws*fs;N,Wn=buttord(omegap,omegas,rp,rs,s);B A=butter(N,Wn,s);b,a=impinvar(B,A,fs);h,w=freqz(b,a,256);h=20*log10(abs(h);plot(w/pi,h);图二程序3wp=0.2*pi;ws=0.5*pi;rp=1;rs=20;fs=1000;omegap=2*fs*tan(wp/2);omegas=2*fs*tan(ws/2);N,Wn=cheb1ord(omegap,omegas,rp,rs,s);B A=cheby1(N,rp,Wn,s);b,a=bilinear(B,A,fs);h,w=freqz(b,a,256);h=20*log10(abs(h);plot(w/pi,h);图三程序4wp=0.2*pi;ws=0.5*pi;rp=1;rs=20;N,Wn=buttord(wp/pi,ws/pi,rp,rs);B A=butter(N,Wn);h,w=freqz(B,A,256);h=20*log10(abs(h);plot(w/pi,h);图四程序5 Wp=0.2*pi;Ws=0.5*pi;Rp=1;Rs=20;T=0.001;Fs=1000;omegap=(2/T)*tan(Wp/2);omegas=(2/T)*tan(Ws/2);N,Wn=cheb1ord(omegap,omegas,Rp,Rs,s);B,A=cheby1(N,Rp,Wn,s);b,a=bilinear(B,A,Fs);h,w=freqz(b,a,256);h1=20*log10(abs(h);plot(w/pi,h1);grid;xlabel(Digital Frequency in pi units);ylabel(Gain in DB);axis(0 1 -50 10);图五程序6 Wp=0.2;Ws=0.5;Rp=1;Rs=20;disp(I)N,Wn=cheb1ord(Wp,Ws,Rp,Rs)B,A=cheby1(N,Rp,Wn);disp();fprintf(%.4en,B);disp();fprintf(%.4en,A);w=linspace(0,0.8*pi,50);h1=20*log10(abs(freqz(B,A,w);plot(w/pi,h1);grid;xlabel(Normalized frequency);ylabel(Gain in DB );axis(0 0.8 -50 1);图六 四、实验小