Matlab filters

AIM:

To verify response of analog Low pass filter (LPF) & High pass filter(HPF) using MATLAB

 

EQUIPMENTS:

Operating System         – Windows XP

Constructor                  - Simulator

Software                      - CCStudio 3 & MATLAB 7.5

THEORY:

Analog Low pass filter & High pass filter are obtained by using butterworth or chebyshev filter with coefficients are given. The frequency – magnitude plot gives the frequency response of the filter.

PROGRAM:

 

Matlab code for filters

%  IIR filters LPF & HPF

clc;

clear all;

close all;

warning off;

disp('enter the IIR filter design specifications');

rp=input('enter the passband ripple');

rs=input('enter the stopband ripple');

wp=input('enter the passband freq');

ws=input('enter the stopband freq');

fs=input('enter the sampling freq');

w1=2*wp/fs;w2=2*ws/fs;

[n,wn]=buttord(w1,w2,rp,rs,'s');

c=input('enter choice of filter 1. LPF 2. HPF \n ');

if(c==1)

    disp('Frequency response of  IIR LPF is:');

[b,a]=butter(n,wn,'low','s');

end

if(c==2)

    disp('Frequency response of  IIR HPF is:');

[b,a]=butter(n,wn,'high','s');

end

w=0:.01:pi;

[h,om]=freqs(b,a,w);

m=20*log10(abs(h));

an=angle(h);

figure,subplot(2,1,1);plot(om/pi,m);

title('magnitude response of  IIR filter is:');

xlabel('(a) Normalized freq. -->');

ylabel('Gain in dB-->');

subplot(2,1,2);plot(om/pi,an);

title('phase response of  IIR filter is:');

xlabel('(b) Normalized freq. -->');

ylabel('Phase in radians-->');