butterl.m

使用Matlab实现了FIR与IIR滤波器

function [ output_args ] = Untitled8( input_args )
%UNTITLED8 Summary of this function goes here
%  Detailed explanation goes here
ft=22050;
Wpl =2*1000/ft;
Wsl= 2*1200/ft;
Rp = 1;
Rs = 100;
[Nl,Wnl] = buttord(Wpl,Wsl,Rp,Rs);
[bl,al] = butter(Nl,Wnl,'low');
[hl,wl]= freqz(bl,al);
subplot(2,2,1);
plot (wl/pi,20*log10(abs(hl)));grid;
xlabel('w/pi'); ylabel('Gain, dB');
title('Type Butter Lowpass Filter');
Wph =2*5000/ft;
Wsh = 2*4800/ft;
Rp = 1;
Rs = 100;
[Nh,Wnh] = buttord(Wph,Wsh,Rp,Rs);
[bh,ah] = butter(Nh,Wnh,'high');
[hh,wh]= freqz(bh,ah);
subplot(2,2,2);
plot (wh/pi,20*log10(abs(hh)));grid;
xlabel('w/pi'); ylabel('Gain, dB');
title('Type Butter highpass Filter');
Wp1b =2*1200/ft;
Wp2b=2*3000/ft;
Ws1b=2*1000/ft;
Ws2b=2*3200/ft;
Wpb=[Wp1b,Wp2b];
Wsb=[Ws1b,Ws2b];
Rp = 1;
Rs = 100;
[Nb,Wnb] = buttord(Wpb,Wsb,Rp,Rs);
[bb,ab] = butter(Nb,Wnb);
[hb,wb]= freqz(bb,ab);
subplot(2,2,3);
plot (wb/pi,20*log10(abs(hb)));grid;
xlabel('w/pi'); ylabel('Gain, dB');
title('Type Butter Bandpass Filter');