clear all
clc
close all
%%
%雷达相关参数
j=sqrt(-1);
c=3e8; %光速
fc=10e9; %载频
lambda=c/fc; %波长
PRF=500; %脉冲重复频率
Tp=3e-6; %LFM信号脉宽
Br=50e6; %LFM信号带宽
Fs=2*Br; %距离向采样频率
Kr=Br/Tp; %调频斜率
betal=70*pi/180; %波束中心下视角 %斜视角
theta=0*pi/180;
H0=20000; %雷达高度
v_x=1000; %导弹沿x轴的速度 匀速直线飞行
D=10; %天线真实孔径
rou_a=D/2; %方位分辨率
rou_r=c/2/Br/(cos(theta)*sqrt(tan(theta).^2+sin(betal).^2)); %距离分辨率
%%
%目标场景
%X0=0; %场景中心的方位向坐标
X0=H0/cos(betal)*tan(theta) ; %场景中心的方位向坐标 20110803修改
Y0=H0*tan(betal); %场景中心的距离向坐标
R0=H0/cos(betal)/cos(theta); %场景中心线到雷达的距离
azirange=100; %方位向成像范围
ranrange=100; %距离向成像范围
Soder_X=50; %方位向点目标间距
Soder_Y=50; %距离向点目标间距
x_range=X0+(-azirange/2:Soder_X:azirange/2); %场景方位向范围
y_range=Y0+(-ranrange/2:Soder_Y:ranrange/2); %场景距离向范围
Ntar=1; %目标个数
target=[0,0,1 %目标相对于场景的坐标(方位坐标 距离坐标 灰度值)
0,1,1
-1,0,1
1,0,1
5,5,1
0,-1,1
];
target(:,1)=target(:,1)*Soder_X;target(:,2)=target(:,2)*Soder_Y+Y0; %目标在绝对坐标系中的坐标
order=target;
%%
%方位向采样,
fdr=-2*v_x^2*fc/c/R0;
Ba=v_x/rou_a ; %满足要求分辨率所需要的多普勒带宽
TT=Ba/abs(fdr); %成像积累时间
Lsar=v_x*TT %合成孔径长度
Tc1=TT+azirange/v_x; %一次成像时间;包括成像区域
Na1=ceil(Tc1*PRF); %一次成像时间内需要的采样点
Na=2^nextpow2(Na1); %为了后面FFT,将Na设置为2的整数次方个
PRF=Na/Tc1; %刷新脉冲重复周期
fangwei=linspace(-azirange/2-Lsar/2-X0,azirange/2+Lsar/2-X0,Na); %20110803 修改
Tm=linspace(-Tc1/2,Tc1/2,Na)-X0/v_x; %方位向慢时间 %20110803 修改
x_rader=Tm*v_x; %雷达方位向历程
fu=linspace(-PRF/2,PRF/2,Na); %多普勒域
%%
%距离向采样
%Rmin=R0-(ranrange/2)*sin(beta) %最小照射距离
Rmin=R0-(ranrange/2)*sin(betal) %20110803改
%Rmax=sqrt((R0+(ranrange/2)*sin(beta))^2+(Lsar/2)^2) %最大照射距离
Rmax=sqrt((R0*sec(theta)+(ranrange/2)*sin(betal))^2+(azirange+Lsar/2)^2) %20110803改
Nr=ceil((2*(Rmax-Rmin)/c+Tp)*Fs); %距离向采样点数
Nr=2^nextpow2(Nr); %为FFT,2的整数次方个
% Rrmx=zeros(1,Na);
% Rrmn=zeros(1,Na);
% for i=1:Na
% Rrmx(i)=max(sqrt((xn-x_rader(i)).^2+(Y0+Y0ch-y_rader(i)).^2+(z_rader(i))^2));
% Rrmn(i)=min(sqrt((xn-x_rader(i)).^2+(Y0-Y0ch-y_rader(i)).^2+(z_rader(i))^2));
% end
% Rmax=max(Rrmx) %最大照射距离
% Rmin=min(Rrmn) %最小照射距离
% Nr=ceil((2*(Rmax-Rmin)/c+Tp)*Fs); %距离向采样点数
dt=(2*Rmax/c-2*Rmin/c+Tp)/Nr; %重新采样
Fs=1/dt; %刷新采样频率
fr=linspace(-Fs/2,Fs/2,Nr); %距离频域
t=(0:Nr-1)*1/Fs; %距离时域
juli=linspace(-ranrange/2,ranrange/2,Nr);
%%
%%下面是回波模拟
%stt=rectpuls(t-Tp/2,Tp).*exp(j*2*pi*(0.5*Kr*(t-Tp/2).^2)); %%定义发射波
t=2*Rmin/c+t;
%wa=zeros(1,Na);
sr=zeros(Na,Nr);
for k=1:Na
sr(k,:)=zeros(1,Nr);
for i=1:Ntar
if abs(v_x*Tm(k)+X0-order(i,1))<Lsar/2
r(k)=sqrt((order(i,1)-x_rader(k))^2+(order(i,2))^2+H0^2);
tr=2*r(k)/c;
%wa(k)=rectpuls(Tm(i),TT); %-order(i,2)*Soder*tan(pha)???
wr=rectpuls(t-Tp/2-tr,Tp);
s=order(i,3)*wr.*exp(j*2*pi*(0.5*Kr*(t-Tp/2-tr).^2-fc*tr));
sr(k,:)=sr(k,:)+s;
end
end
end
s=sr.';
%Jr=qipian(Na,Nr,Lsar,Tm,order,x_rader,t,Ntar,v_x,X0,H0,c,lambda,Tp,Kr,fc);
%s=s+Jr;
SAREcho=strcat('huiboshuju.mat');
save(SAREcho,'s');
%sat=rectpuls(Tm,Tc1).*exp(j*pi*4*v_x^2*Tm^2/lambda/R0);
% figure(1)
% plot_img(fangwei,juli,s,30),grid on
% title('原始回波数据');
% xlabel('方位维范围');ylabel('距离维范围');
%%
%CS成像
pi2=2*pi;
wc =2*pi*fc;
DeltaR = c/(2*Fs);
%Xc = Xmin+DeltaR*ran_num/2; % Range distance to center of target area
X0 = DeltaR*Nr/2; % Target area in range is within [Xc-X0,Xc+X0]
Y0 = Na*v_x/PRF/2; % Target area in cross-range is within [Yc-Y0,Yc+Y0]
% Rmin=Xc-0.5*ran_num*DeltaR;
% Rmax=Xc+0.5*ran_num*DeltaR;
Xc = R0;
Rc=Xc;
Ts=(2/c)*Rmin; % start time of sampling
% Tf=(2/C)*Rmax;
Rref=Xc;
tm = ((0:Na-1) -Na/2)/PRF;
t=Ts+(0:Nr-1)*dt; %回波时间加上集体的延迟时间
x = Rmin+(0:Nr-1)*DeltaR;
%x=linspace(Rmin,Rmax,Nr)
%%cross-range:y domain
%y = linspace(-ranrange/2,ranrange/2,Nr); %y域序列:-Y0~Y0
y=linspace(-azirange/2-Lsar/2,azirange/2+Lsar/2,Na); %20110803修改
Deltay = v_x/PRF;
%kyc = 0; %20110803
kyc = 4*pi/lambda*sin(theta);
dky = pi2/(Na*Deltay);
ky = dky*(-Na/2:Na/2-1)+kyc;
%%range:x domain
dw = pi2/(Nr*dt); % Frequency domain sampling
w = dw*(-Nr/2:Nr/2-1); %(魏改:去掉载频wc)
fr = w./pi2;
%fac = 0; %20110803
fac = 2*v_x*sin(theta)/lambda;
fa = (-Na/2:Na/2-1)*(PRF/Na)+fac;
kxc = 4*pi/lambda;
phi0 = sqrt(kxc^2-ky.^2);
%Cs = ones(ran_num,1)*(kxc./phi0-1);
Cs = (kxc./phi0-1);%CS因子???
phi1 = phi0./kxc;%cos(theta)
phi2 = (ky./kxc).^2;%sin(theta)^2
temp1 = 2*lambda*Xc./c^2;
%gamae = ones(ran_num,1)*(1./(1/gama-temp1.*phi2./(phi1.^3)));
gamae = (1./(1/Kr-temp1.*phi2./(phi1.^3)));%等效调频斜率
%fac = 0; %20110803
fac = 2*v_x*sin(theta)/lambda;
s=s.*exp(-j*2*pi*fac*ones(Nr,1)*tm);
%%CSA:7 steps
%s=fftshift(fft(fftshift(s).')).';
s = fty(s);%方位向FFT
t = t.';
%Chirp Scaling 线频调变标处理
for idx = 1:Nr
H1 = exp(j*pi*Cs.*gamae.*(t(idx)-2*(Xc*(1+Cs))./c).^2);
s(idx,:) = s(idx,:).*H1;
end
clear H1;
s = ftx(s);%距离向FFT
for idx = 1:Na
H2 = exp(j*pi*(fr.^2')./(1+Cs(idx))./gamae(idx)...
+j*4*pi/c*Rc*Cs(idx).*(fr')); %距离向匹配滤波&距离迁移校正
s(:,idx) = s(:,idx).*H2;
end
clear H2;
%距离向IFFT
s = iftx(s);
for idx = 1:Nr
H3 = exp(j*4*pi/c^2*gamae.*Cs.*(1+Cs).*(((x(idx)-Xc).^2))...
+j*4*pi/lambda*x(idx)*phi1);%消除误差函数,方位向匹配滤波
s(idx,:) = s(idx,:).*H3;
end
clear H3;
clear gamae Cs;
%方位向IFFT
s = ifty(s);
figure(3)
imagesc(x,y,abs(s))
colormap(gray)
Rb = x;
figure;
colormap(gray(256));
G=abs(s).';
xg=max(max(G)); ng=min(min(G)); cg=255/(xg-ng);
%%%%%%%%%%%%%%%%%%%%%% 注意下面成像用的坐标是y,不是Yc+y
Brightness = 2;
axis xy;
%yidongliang=round((x-Rc)*0*PRF/v_x);%%%%用这一句比下一句校正的好
yidongliang=round((x-Rc)*sin(theta)*PRF/v_x);%20110803修改
% yidongliang=round((X-Rc)*tan(theta_c)*PRF/v) ;
for i=1:Nr
G(:,i)=circshift(G(:,i),yidongliang(i));
end
% image(x,f
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