FIR Digital Filter using rectangular Window technique

This section of MATLAB source code covers FIR low pass and high pass filter using rectangular method.

FIR Low Pass Filter MATLAB Code

clc;

close all;

clear all;

format long;

rp=input('enter the passband ripple:(default:0.04)');

rs=input('enter the stopband ripple:(default: 0.05)');

fp=input('enter the passband frequency:(default:1500)');

fs=input('enter the stopband frequency:(default:2000)');

f=input('enter the sampling frequency:(default:9000)');

wp=2*(fp/f);

ws=2*(fs/f);

num=-20*log10(sqrt(rp*rs))-13;

dem=14.6*(fs-fp)/f;

n=ceil(num/dem);

n1=n+1;

if(rem(n,2)~=0)

n1=n;

n=n-1;

end;

y=boxcar(n1);

%Lowpass filter

b=fir1(n,wp,y);

[h,o]=freqz(b,1,256);

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

subplot(2,1,1);

plot(o/pi,m);

ylabel('gain in db---->');

xlabel('Normalised frequency---->');

title('FIR filter using Rectangular window of LPF ----');

grid on;

FIR High Pass Filter MATLAB Code

%Highpass filter

b=fir1(n,wp,'high',y);

[h,o]=freqz(b,1,256);

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

subplot(2,1,2);

plot(o/pi,m);

ylabel('gain in db---->');

xlabel('Normalised frequency---->');

title('FIR filter using Rectangular window of HPF ----');

title('Magnitude response of high pass filter');

grid on;

Output plot

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