lvboqi.m

巴特沃斯滤波器设计

clc
clear
clear all
%系统指标描述
wp=0.2*pi;wr=0.3*pi;ap=1;ar=15;T=1;
wap=wp/T;war=wr/T;
%求巴特沃兹模拟低通滤波器原型
[n,wn]=buttord(wap,war,ap,ar,'s');
[b,a]=butter(n,wn,'s')
[db,mag,pha,Omega]=freqs_m(b,a);
subplot(234);plot(Omega/pi,mag);title('模拟滤波器幅度响应|Ha(j\Omega)|');
%脉冲响应不变法设计巴特沃兹滤波器
[bz,az]=impinvar(b,a,1/T)
%巴特沃兹数字滤波器的脉冲响应
[h,n]=impz(bz,az);
[db,mag,pha,grd,w]=freqz_m(bz,az);
subplot(231);plot(w/pi,mag);title('数字滤波器幅度响应|Ha(j\Omega)|');
subplot(232);plot(w/pi,db);title('数字滤波器幅度响应(dB)');
subplot(233);plot(w/pi,pha/pi);title('数字滤波器相位响应');
subplot(235);plot(n,h);title('脉冲响应');
a_w=2*pi/1000;
ap=-(min(db(1:1:wap/a_w+1)))
as=-round(max(db(war/a_w+1:1:501)))