main2.m

用matlab编写的雷达系统信号仿真程序

close all;clear all;clc;
%%%%%%%%%%产生雷达发射信号%%%%%%%%%%
code=[1,1,1,1,1,-1,-1,1,1,-1,1,-1,1];      % 13位巴克码
tao=10e-6;    % 脉冲宽度10us
fc=28e6;      %调频信号起始频率
f0=30e6;
fs=100e6;     %采样频率100MHz
ts=1/fs;
B=4e6;       %调频信号带宽
t_tao=0:1/fs:tao-1/fs;
N=length(t_tao);
k=B/fs*2*pi/max(t_tao);
n=length(code);
pha=0;

s=zeros(1,n*N);
for i=1:n
  if code(i)==1
pha=pi;
  else pha=0;
  end
  s(1,(i-1)*N+1:i*N)=cos(2*pi*fc*t_tao+k*cumsum(t_tao)+pha);
end
t=0:1/fs:13*tao-1/fs;
figure(1),subplot(2,1,1),plot(t,s),
xlabel('t(单位：s)'),title('混合调制信号（13位巴克码＋线性调频）');
s_fft_result=abs(fft(s(1:N)));
subplot(2,1,2),plot((0:fs/N:fs/2-fs/N),abs(s_fft_result(1:N/2)));
xlabel('频率（单位：Hz）'),title('码内信号频谱');
%%%%%%%%%%产生脉冲压缩系数%%%%%%%%%%
%-----------正交解调-----------------%
N=tao/ts;
n=0:N-1;
s1=s(1:N);
local_oscillator_i=cos(n*f0/fs*2*pi);    %I路本振信号
local_oscillator_q=sin(n*f0/fs*2*pi);    %q路本振信号
fbb_i= local_oscillator_i.*s1;          %I路解调
fbb_q= local_oscillator_q.*s1;         %q路解调
window=chebwin(51,40);          %这是采用50阶cheby窗的FIR低通滤波器
[b,a]=fir1(50,2*B/fs,window);
fbb_i=[fbb_i,zeros(1,25)];
fbb_q=[fbb_q,zeros(1,25)];
fbb_i=fbb_i(26:end);              %截取有效信息
fbb_q=fbb_q(26:end);             %截取有效信息
fbb=fbb_i+fbb_q;

%-----------产生理想线性调频脉冲压缩匹配系数-----------------%
M=131126;    %因为回波信号数据长度为3600点，所以利用FFT，做4096点FFT
D=B*tao;
match_filter_1=ts*fliplr(conj(fbb))*sqrt(D)*2/tao;
match_filter_1_fft=fft(match_filter_1,M);    %第一次脉冲压缩处理匹配系数
figure(2),subplot(2,1,1),plot(real(match_filter_1_fft)),title('脉冲压缩系数（实部）');
subplot(2,1,2),plot(imag(match_filter_1_fft)),title('脉冲压缩系数（虚部）');

N=length(s)
n=0:N-1;
local_oscillator_i=cos(n*f0/fs*2*pi);    %I路本振信号
local_oscillator_q=sin(n*f0/fs*2*pi);    %q路本振信号
fbb_i= local_oscillator_i.*s;           %I路解调
fbb_q= local_oscillator_q.*s;          %q路解调
window=chebwin(51,40);          %这是采用50阶cheby窗的FIR低通滤波器
[b,a]=fir1(50,0.5,window);
fbb_i=[fbb_i,zeros(1,25)];
fbb_q=[fbb_q,zeros(1,25)];
fbb_i=filter(b,a,fbb_i);
fbb_q=filter(b,a,fbb_q);
fbb_i=fbb_i(26:end);              %截取有效信息
fbb_q=fbb_q(26:end);             %截取有效信息
signal=fbb_i+j*fbb_q;
clear fbb_i;
clear fbb_q;

signal_fft=fft(signal,M);
pc_result_fft=signal_fft.*match_filter_1_fft;
pc_result=ifft(pc_result_fft,M);
figure(3),plot((0:ts:length(signal)*ts-ts),pc_result(1:length(signal))),
xlabel('时间，单位：s'),title('回波脉冲压缩处理结果');

clear local_oscillator_i;
clear local_oscillator_q;

t=tao*length(code);
match_filter_2=2*ts*fliplr(conj(pc_result))*2/t;
match_filter_2_fft=fft(match_filter_2,M);    %第二次脉冲压缩处理匹配系数
figure,subplot(2,1,1),plot(real(match_filter_2_fft)),title('脉冲压缩系数(实部)') ;
subplot(2,1,2),plot(imag(match_filter_2_fft)),title('脉冲压缩系数(虚部)');
clear fbb;
clear match_filter_1;
clear match_filter_2;
clear signal;
clear signal_fft;
clear pc_result;
clear pc_result_fft;

%%%%%%%%%%产生雷达回波%%%%%%%%%%
f_frame=1e3;          %雷达发射信号重频，单位：Hz
T_frame=1/f_frame;
N_echo_frame=18;

f_doppler=3.5e3;     %动目标的多普勒频率
t_frame=0:ts:T_frame-ts;
t_mobj=200e-6;      %动目标位置
echo_mobj_pulse=[zeros(1,t_mobj/ts),s,zeros(1,(T_frame-t_mobj)/ts-length(s))];
echo_mobj=repmat(echo_mobj_pulse,1,N_echo_frame);
t_doppler=0:ts:N_echo_frame*T_frame-ts;
s_doppler=cos(2*pi*f_doppler*t_doppler);
s_echo_mobj=echo_mobj.*s_doppler;

t_fobj=450e-6;       %固定目标位置
echo_fobj_pulse=[zeros(1,t_fobj/ts),s,zeros(1,(T_frame-t_fobj)/ts-length(s))];
s_echo_fobj=repmat(echo_fobj_pulse,1,N_echo_frame);

t_clutter=700e-6;     %杂波位置
t_clutter_pulse=39e-6;
sigma=2;            %瑞利分布参数sigma;
t1=0:ts:t_clutter_pulse-ts;
rand('state',0);       %把均匀分布伪随机发生器置为0状态
u=rand(1,length(t1));
echo_clutter=0.08*sqrt(2*log(1./u))*sigma;%.*s;      %产生瑞利分布信号1
s_echo_clutter_pulse=[zeros(1,t_clutter/ts),echo_clutter,zeros(1,(T_frame-t_clutter)/ts-length(echo_clutter))];
s_echo_clutter=repmat(s_echo_clutter_pulse,1,N_echo_frame);

s_noise=0.1*rand(1,N_echo_frame*T_frame/ts);

s_echo=s_echo_mobj+s_echo_fobj+s_echo_clutter+s_noise;
clear s_echo_mobj;
clear s_echo_fobj;
clear s_echo_clutter;
clear s_echo_clutter_pulse;
clear s_noise;
clear echo_mobj_pulse;
clear echo_mobj;
clear echo_fobj_pulse;
clear echo_clutter;
clear s_doppler;
clear t_doppler;
%-------------正交解调---------------%
N=N_echo_frame*T_frame/ts;
n=0:N-1;
local_oscillator_i=cos(n*f0/fs*2*pi);      %I路本振信号
local_oscillator_q=sin(n*f0/fs*2*pi);    %q路本振信号
s_echo_i=local_oscillator_i.*s_echo;    %I路解调
s_echo_q=local_oscillator_q.*s_echo;   %q路解调
window=chebwin(51,40);        %这是采用50阶cheby窗的FIR低通滤波器
[b,a]=fir1(50,2*B/fs,window);
s_echo_i=[s_echo_i,zeros(1,25)];
s_echo_q=[s_echo_q,zeros(1,25)];
s_echo_i=filter(b,a,s_echo_i);
s_echo_q=filter(b,a,s_echo_q);
s_echo_i=s_echo_i(26:end);           %截取有效信息
s_echo_q=s_echo_q(26:end);          %截取有效信息
s_echo_mf=s_echo_i+j*s_echo_q;
clear s_echo;
clear local_oscillator_i;
clear local_oscillator_q;
clear s_echo_i;
clear s_echo_q;
clear n;
%%%%%%%%脉冲压缩处理%%%%%%%%
for i=1:N_echo_frame
  s_echo_fft_result=fft(s_echo_mf(1,(i-1)*T_frame/ts+1:i*T_frame/ts),M);
  s_pc_fft_1=s_echo_fft_result.*match_filter_1_fft;
  s_pc_fft_2=s_pc_fft_1.*match_filter_2_fft;
  s_pc_result(i,:)=ifft(s_pc_fft_2,M);
end
clear s_echo_mf;

s_pc_result_1=s_pc_result';
s_pc_result_1=reshape(s_pc_result_1,1,N_echo_frame*M);
figure;
subplot(2,1,1);
size(0:ts:N_echo_frame*T_frame-ts)
size(real(s_pc_result_1))
plot(0:ts:N_echo_frame*T_frame-ts,real(s_pc_result_1)),
xlabel('t(单位：s)'),title('脉冲压缩处理后结果（实部）');
subplot(2,1,2);
plot(0:ts:N_echo_frame*T_frame-ts,imag(s_pc_result_1)),
xlabel('t(单位：s)'),title('脉冲压缩处理后结果（虚部）');

%%%%%%%%固定杂波对肖处理%%%%%%%%%
for i=1:16
  s_MTI_result(i,:)=s_pc_result(i,:)+s_pc_result(i+2,:)-2*s_pc_result(i+1,:);
end

clear s_pc_result;
clear s_pc_result_1;
s_MTI_result_1=s_MTI_result';
s_MTI_result_1=reshape(s_MTI_result_1,1,(N_echo_frame-2)*M);
figure,subplot(2,1,1),plot(0:ts:N_echo_frame*T_frame-ts,real(s_MTI_result_1));
slabel('t(单位：s)'),title('固定杂波对消后结果(实部)');
subplot(2,1,2),plot(0:ts:N_echo_frame*T_frame-ts,imag(s_MTI_result_1));
slabel('t(单位：s)'),title('固定杂波对消后结果(虚部)');
clear s_MTI_result_1;

%%%%%%%%%%MTD处理和求模%%%%%%%%%%%
for i=1:T_frame/ts
  s_MTD_result_1(:,i)=fft(s_MTI_result(:,i),16);
end
for i=1:T_frame/ts
  s_MTD_result(i)=abs(max(s_MTD_result));
end

figure,plot(0:ts:N_echo_frame*T_frame-ts,s_MTD_result),
xlabel('t(单位：s)'),title('MTD处理后求模结果(信号最大通道)');

%%%%%%%%CFAR处理%%%%%%%%