# 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;

## Useful Links to MATLAB codes

Refer following as well as links mentioned on left side panel for useful MATLAB codes.
OFDM Preamble generation  Time off estimation corr  Freq off estimation corr  channel estimation  11a WLAN channel  PN sequence generation  OFDMA Tx Rx  AES DES  carrier aggregation  CCDF  FIR Filter  IIR Filter  Low Pass FIR  Viterbi decoder  CRC8 CRC32