Question

Design a 100th-order bandpass FIR filter using the window method (fir2) to cut frequencies below 15Hz and above 30 Hz in an application where the sampling frequency is 125 Hz. Plot the filter coefficients that defining the filter (stem). Plot the frequency response of the FIR filter designed (freqz)

Answer 1

MATLAB Code:

clc;
clear all;
close all;

N = 100; % Order = 100
fl = 15; % Lower Cut off Frequency
fh = 30; % Higher Cut off Frequency
fs = 125; % Sampling Frequency

wl = 2*fl/fs; % Digital Lower Cut off Frequency in pi units
wh = 2*fh/fs; % Digital Higher Cut off Frequency in pi units

w = [0, wl, wh, 1]; % The frequency vector
m = [0, 1, 1, 0]; % The magnitude for Band Pass Filter

h = fir2(100,w,m); % Finding the filter coefficients

n = 0:100; % Range of n for order 100

stem(n,h,'linewidth',2);
grid;
xlabel('n');
ylabel('Amplitude');
title('Filter Coefficients');

figure
freqz(h,1); % Plot the frequency response

After executing, we get