%
%
% dt = 1/100; % sampling rate
% et = 4; % end of the interval
% t = 0:dt:et; % sampling range
% y = 3*sin(4*2*pi*t) + 5*sin(2*2*pi*t);
%
% Y = fft(y); % compute Fourier transform
% n = size(y,2); % 2nd half are complex conjugates
% amp_spec = abs(Y)/n;
%
%
% figure;
% subplot(3,1,1); % first of two plots
% plot(t,y); grid on % plot with grid
% axis([0 et -8 8]); % adjust scaling
%
% subplot(3,1,2); % second of two plots
% freq = (0:size(amp_spec,2)-(1/(n*dt)))/(n*dt); % abscissa viewing window
% plot(freq,amp_spec); grid on
%
% subplot(3,1,3); % second of two plots
% freq1 = ((-size(amp_spec,2)+1)/2:(size(amp_spec,2)-1)/2)/(n*dt); % abscissa viewing window
% FTy = fftshift(amp_spec)
% plot(freq1,FTy); grid on
%

clear all close all clc x=[] for i = -5:1/1000:5 if i > 0.5 | i < -0.5 x = [x 0]; else x = [x 1]; end end figure;plot(-5:1/1000:5,x)

dt = 1/1000;
Xf1 = fft(x); n= length(Xf1);
Xf = abs(Xf1)/n;

Freq = (0:size(Xf,2)-1)/(n*dt) figure; plot(Freq ,Xf)

freq1 = ((-size(Xf,2)+1)/2:(size(Xf,2)-1)/2)/(n*dt)
Xf = fftshift(Xf) figure; plot(freq1,Xf)

f=[-2:0.01:2]
H1 = 1./sqrt(1 + (f/1).^2); figure;plot(f,H1); H = 1./sqrt(1 + (freq1/100).^2);
REP_mod = H.* Xf; figure;plot(freq1,abs(REP_mod)); Xf1 = fftshift(Xf1)

REP = H.*Xf1;

REP = ifftshift(REP);

IXF = ifft(REP);
%IXF = abs(IXF);

figure; plot(-5:1/1000:5,IXF)