clear;
close all;
clc;
%% 程序说明
% 双频点连续波雷达(无调制信息)
%% 参数设置
% 信号参数
df = 100;
fc1 = 3e3-df/2;
fc2 = 3e3+df/2;
c = 3e8;
lambda= c/fc1;
T = 4e-3;
fs = 100e3;
t = 0:1/fs:T;
N = 3000*length(t);
f = linspace(-fs/2,fs/2,N);
% 目标参数
R0 = 50e3;
v = 1e3;
Rt =R0+v*t;
%% 信号模型
% 发射信号
st1 = exp(1j*2*pi*fc1*t);
st2 = exp(1j*2*pi*fc2*t);
% 接收信号
rt1 = exp(1j*2*pi*fc1*(t-2*Rt/c));
rt2 = exp(1j*2*pi*fc2*(t-2*Rt/c));
% 混频后信号
yt1 = rt1.*conj(st1);
rf1 = fftshift(fft(yt1,N));
[~,I1] = max(abs(rf1));
phi1 = angle(rf1(I1));
% 混频后信号
yt2 = rt2.*conj(st2);
rf2 = fftshift(fft(yt2,N));
[~,I2] = max(abs(rf2));
phi2 = angle(rf2(I2));
figure;
plot(f,abs(rf1));
xlabel('频率(Hz)');
figure;
plot(f,abs(rf2));
xlabel('频率(Hz)');
%% 相位差
yt = yt2.*conj(yt1);
phi = angle(yt);
figure;
plot(t,phi);
xlabel('时间(s)');
ylabel('相位差(rad)');
figure;
plot(t,-phi/2/pi/df*c/2);
xlabel('时间(s)');
ylabel('距离(m)');
% figure;
% plot(t,real(st));
% xlabel('时间(s)');
% title('发射信号波形');
% figure;
% plot(t,real(rt));
% xlabel('时间(s)');
% title('接收信号波形');
% figure;
% plot(t,real(yt));
% xlabel('时间(s)');
% title('混频后信号波形');
%
% figure;
% plot(f,abs(rf));
% xlabel('频率(Hz)');
% figure;
% plot(V,abs(rf));
% xlabel('速度(m/s)');