%距离估计实验 匹配滤波器估计时延差
clear all;close all;clc;
C = 1450;
T = 0.05; % 50ms脉宽
TL = 1; % 1s周期
F1 = 5000; % 起始频率5kHz
F2 = 8000; % 终止频率8kHz
K = (F2- F1)/T; % 调频系数
jay = sqrt(-1);
FS = 80000; % 采样率200kHz
N = round(FS*T); % 采样点数
t = (0:N-1)/FS;
NL = round(FS*TL);
%% 产生LFM信号
signal = exp(jay*(2*pi*F1*t+pi*K*(t.^2)));
s = [zeros(1,2000) real(signal) zeros(1,2000)];
figure(1),subplot(211)
plot((0:length(s)-1)/FS,s);
axis([0 length(s)/FS -1.2 1.2]);grid on;set(gcf,'color','white');
xlabel('时间t/s'),ylabel('信号s(t)/V'),title('发射机调频信号');
%% 回波信号响应
h = s(length(s):-1:1); % 单位脉冲响应h(t)=s(0.1-t);
tao = 0.007; % 回波延时7ms,共延时0.107秒
N_tao = round(tao*FS);
echo = [zeros(1,N_tao) s];
h = [h zeros(1,N_tao)];
figure(1),subplot(212)
plot((0:length(echo)-1)/FS,echo);
axis([0 length(echo)/FS -1.2 1.2]);grid on;set(gcf,'color','white');
xlabel('时间t/s'),ylabel('信号echo(t)/V'),title('接收机调频信号');
y = conv(echo,h);
figure(2)
plot((0:length(y)-1)/FS,y);
grid on;set(gcf,'color','white');
xlabel('时间t/s'),ylabel('信号y(t)/V'),title('匹配滤波器输出信号');
[ymax i] = maxi(y,(1:length(y)));
TAO = (i-1)/FS-0.1
