clc; clear;

configure_parameters;
global s_T s_R c

% 频域上的匹配滤波
s_T_fft = fft(s_T);
s_R_fft = fft(s_R);
s_R_fft_conj = conj(s_R_fft);

matched_filter = ifft(s_T_fft .* s_R_fft_conj);
[~, peak] = max(matched_filter);
t_delay = 1 - peak / length(matched_filter);
d = (c * t_delay) / 2;

fprintf("r = %f, predict d = %f\n", r_0, d);
fprintf("eps = %f\n", abs(r_0 - d));

figure(1);
subplot(311);
plot(freqs, abs(s_T_fft));
title("Chirp signal");
subplot(312);
plot(freqs, abs(s_R_fft));
title("Received Chirp signal");
subplot(313);
plot(freqs, abs(s_T_fft .* s_R_fft_conj));
title("Matcher filter");

figure(2);
subplot(311);
plot(t, s_T);
title("Chirp signal");
subplot(312);
plot(t, s_R);
title("Received Chirp signal");
subplot(313);
plot(t, matched_filter);
title("After matched filter");