BUTTERWORTH IIR FILTERS USING MATLAB

MATLAB PROGRAM FOR IIR:

To write a program for IIR(inite Impulse Response) filter like Low pass FIR filter, High pass FIR filter, Band pass FIR filter and Band stop FIR filter using Rectangular window using MATLAB.

ALGORITHM:

LOW PASS FILTER:

Step 1: Read the input sequence
Step 2: Perform low pass filter calculations
Step 3: Plot the output sequences

HIGH PASS FILTER:

Step 1: Read the input sequence
Step 2: Perform high pass filter calculations
Step 3: Plot the output sequences

BAND PASS FILTER:

Step 1: Read the input sequence
Step 2: Perform band pass filter calculations
Step 3: Plot the output sequences

BAND STOP FILTER:

Step 1: Read the input sequence
Step 2: Perform band stop filter calculations
Step 3: Plot the output sequences

PROGRAM:
clc;
clear all;
close all;
rp= input ('Enter the passband ripple ');
rs= input('Enter the stop band ripple ');
wp= input('Enter the passband frequency ');
ws=input('Enter the stopband frequency ');
fs=input('Enter the sampling frequency ');
w1=2*wp/fs;
w2=2*ws/fs;
[n,wn]=buttord(w1,w2,rp,rs);
[b,a]=butter(n,wn);
w=0:0.01:pi;
[h,om]=freqz(b,a,w);
m=20*log10(abs(h));
an=angle(h);
subplot(2,1,1);
plot(om/pi,m);
title('IIR LPF');
ylabel('Gain(dB)');
xlabel('Normalised frequency');
subplot(2,1,2);
 plot(om/pi,an);
 ylabel('Phase(radians)');
 xlabel('Normalised frequency');


OUTPUT:

        
                                 Fig: IIR window Output



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