Add experiment

1 - experiment/Chirp/Test.m

@@ -0,0 +1,20 @@
+N = 1e3 + 1;
+f_c = 1e6;
+t = linspace(0, pi / f_c, N);
+f_s = 1 / N;
+freqs = (0:N-1) / f_s;
+x = exp(-1j * 2 * pi * f_c * t);
+
+subplot(211);
+plot(t, imag(x));
+title("x(t) = sin(t)");
+xlabel("t");
+ylabel("x(t)");
+
+x_fft = abs(fft(imag(x)));
+subplot(212);
+plot(t, x_fft);
+title("X(f) = fft(x(t))");
+xlabel("f");
+ylabel("X(f)");
+

1 - experiment/Chirp/compress.m

@@ -0,0 +1,17 @@
+clc; clear;
+
+configure_parameters;
+global s_T s_R
+
+compressed_signal = conv(s_R, fliplr(s_T), 'same');
+
+figure(1);
+subplot(311);
+plot(t, s_T);
+title("Chirp signal");
+subplot(312);
+plot(t, s_R);
+title("Received Chirp signal");
+subplot(313);
+plot(t, compressed_signal);
+title("Matcher filter");

1 - experiment/Chirp/configure_parameters.m

@@ -0,0 +1,21 @@
+global f_s T_r simu_time t start_freq end_freq c len r_0 freqs s_T s_R
+
+f_s = 1e4;
+T_r = 1 / f_s;
+simu_time = 1;
+t = linspace(0, simu_time, f_s);
+start_freq = 0;
+end_freq = 1e7;
+c = 3e8;
+r_0 = 8e6;
+
+s_T = chirp(t, start_freq, simu_time, end_freq, 'linear') * 10;
+len = length(s_T);
+freqs = linspace(-f_s / 2, f_s / 2, len);
+
+s_R = zeros(size(s_T));
+delay = 2 * r_0 / c;
+delay_samples = round(delay * len) + 1;
+s_R(delay_samples:len) = 0.8 * s_T(1:len-delay_samples + 1);
+s_R = awgn(s_R, 1);
+

1 - experiment/Chirp/frequency_domain.m

@@ -0,0 +1,39 @@
+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");

1 - experiment/Chirp/time_domain.m

@@ -0,0 +1,24 @@
+clc; clear;
+
+configure_parameters;
+global s_T s_R c
+
+% 时域上的匹配滤波
+matched_filter = conv(s_R, fliplr(s_T), 'same');
+[~, peak] = max(matched_filter);
+t_delay = peak / length(matched_filter) - 0.5;
+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(t, s_T);
+title("Chirp signal");
+subplot(312);
+plot(t, s_R);
+title("Received Chirp signal");
+subplot(313);
+plot(t, matched_filter);
+title("Matcher filter");