% =====================================================
% 
%   Herramientas de representación tiempo-frecuencia
%  Facultad de Ingeniería, Universidad de la República
% 
%   clase de práctico 1
% 
% autor: martín rocamora
%        <rocamora@fing.edu.uy>
% fecha: mayo 2017
% 
% =====================================================

addpath('./tftb-0.2/mfiles/')

close all
clear all

%  ----------------------------------------------------------------------------
%                         LINEAR FREQUENCY MODULATION
%  ----------------------------------------------------------------------------

% generate a chirp signal
n_points = 128;
fmin = 0.0; fmax = 0.5;
signal = fmlin(n_points, fmin, fmax);
% noisy chirp
% signal = sigmerge(signal, noisecg(n_points), 0);

% compute the energy spectrum of the chirp
dsp1 = fftshift(abs(fft(signal)).^2);

% compute Wigner-Ville distribution of the chirp.
[tfr,t_tfr,f_tfr] = tfrwv(signal);

%  ----------------------------------------------------------------------------
%                                    PLOTS
%  ----------------------------------------------------------------------------

figure()
% subplot(2, 1, 1)
plot(real(signal))
xlim([0, n_points])
title('Linear Frequency Modulation')
ylabel('Real Part')
xlabel('Time')
grid()

figure()
% subplot(2, 1, 2)
plot((-n_points/2:n_points/2-1)/n_points, dsp1)
xlim([-0.5, 0.5])
title('Spectrum')
ylabel('Squared modulus')
xlabel('Normalized Frequency')
grid()

figure()
% imagesc(t_tfr, f_tfr, tfr)
% axis xy
levels = 5;
contour(t_tfr, f_tfr, tfr, levels)
xlabel('Time')
ylabel('Normalized Frequency')