matlab_SAR回波生成和成像程序，可用于任意波段产生合成孔径雷达的回波和成像仿真

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% %%%% Generate SAR echo data %%%% %%%% float 32 ompact format %%%% %%%% the data is written in a file named sarecho.mat %%%% %%%% V2.0 2010-7-6 revised by Cooper can adopt manuvers path %%%% %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% clear;clc; cj=sqrt(-1); c=299792458; %light speed Tp=4e-6; %pulse width fc=1000e6; B=50e6; %trasmit LFM signal bandwidth fs=200e6; %sample frequency PRF=200; %pulse repeat frequency Res_r=c/2/B; %resolution in range dimention Res_a=3; %resolution in azimuth dimention theta=2*asin(c/(4*Res_a*fc)); %accumulated angle(radian) K=B/Tp; %调频率 lamda=c/fc; %wave length dt=1/fs; %sample space in time N=ceil(Tp/dt); %sample number in pulse during time dy=c/2*dt; %sample space in range V=50; %velocity in flight direction h=5000; dx=V/PRF; %sample space in azimuth gamma=zeros(20,20); numx=20;numy=20; %number of target gamma(1,1)=1;%gamma(1,5)=1;gamma(1,10)=1;gamma(1,15)=1;gamma(1,20)=1; %gamma(10,1)=1;gamma(10,5)=1;gamma(10,10)=1;gamma(10,15)=1;gamma(10,20)=1; %gamma(20,1)=1;gamma(20,5)=1;gamma(20,10)=1;gamma(20,15)=1;gamma(20,20)=1; detax=10; %distance between targets in azimuth detay=20; %distance between targets in range Range_Swath=numy*dy; Azimuth_Swath=numx*dx; w=numy*detay/2; Rg0=3000; %RB Rgmin=Rg0-w; %RB near Rgmax=Rg0+w; %RB far halfapeture=sqrt(Rg0.^2+h.^2)*tan(theta/2); %half length of an aperture halfapewidth=round(halfapeture/dx); %the sample number of a half aperture imghalfapeture=numx*detax/2; %the half region of a map imghalfaperturewidth=round(imghalfapeture/dx); %半成像采样点数 rpchalfapeturewidth=halfapewidth+imghalfaperturewidth; %方位向半采样点数 rawdatawidth=2*rpchalfapeturewidth+1; %the sample number in azimuth dimension Rmin=sqrt(h.^2+Rgmin^2); %R0 near Rmax=sqrt(h.^2+Rgmax^2); %R0 far delaymin=2*Rmin/c-Tp/2; %距离波门起始时刻 delaymax=2*Rmax/cos(theta/2)/c+Tp/2;%距离波门终止时刻 slicelen=round((delaymax-delaymin)/dt); %the sample number in range dimension Src=sqrt(h.^2+Rg0^2);; %R0 center Rang_Wath=0; Azimuth_StartNum=0; Azimuth_EndNum=0; %%%%%%%雷达平台位置%%%%%%%%%%%%%% X0 = 0; Y0 = 0; Z0 = h; tA = 0.000; %天线相位中心指向成像区域中心的时刻 NumA=-floor(rawdatawidth/2):rawdatawidth-floor(rawdatawidth/2)-1; ta = (NumA/PRF)+tA; azm = zeros(rawdatawidth,3); azm(:,1) = X0+V*ta; azm(:,2) = Y0;%+1*sin(2*ta+0.1); azm(:,3) =Z0;%+5*sin(0.5*ta); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Head=[fc,B,Tp,fs,V,PRF,dx,dy,Res_r,Res_a,theta,Rg0,Rang_Wath,Range_Swath,Azimuth_Swath,h,Rmin,... Src,Rmax,Azimuth_StartNum,Azimuth_EndNum,rawdatawidth,slicelen,lamda];%需要存储的几何参数，共24个 Head(256)=0; % SaveFile='e:\sim\echo.seo'; %回波文件保存地址 % fid=fopen(SaveFile,'w'); %打开回波文件 % fwrite(fid,Head,'float32'); [p,n,g]=find(gamma'); Hwaitbar=waitbar(0,'读入场景...'); Num=length(g); for i=1:Num % tar(i,1)=(p(i)-numx/2)*detax;tar(i,2)=Rg0+(n(i)-numy/2)*detay;tar(i,3)=gamma(n(i),p(i));tar(i,4)=0; tar(i,1)=0;tar(i,2)=Rg0;tar(i,3)=gamma(n(i),p(i));tar(i,4)=0; waitbar(i/Num); end close(Hwaitbar); Hwaitbar=waitbar(0,'产生回波...'); sr=zeros(rawdatawidth,slicelen); for i=1:rawdatawidth %首先判断该方位向位置时，波束覆盖范围是否包含点目标， temp=zeros(1,slicelen);%距离向初始化 for m=1:Num %在方位向i时，雷达与目标位置之间的距离，以成像区域中间位置作为坐标原点 r=sqrt((azm(i,2)-tar(m,2))^2+azm(i,3)^2); dazimuth=azm(i,1)-tar(m,1); %判断点目标m是否在波束覆盖范围之内 if(abs(dazimuth)>r*tan(theta/2)) temp=temp; else %接收到点目标的延迟时间，以最先接收到的回波延时作为参考 delaym=2*sqrt(dazimuth.^2+r^2)/c-Tp/2-delaymin; %接收到信号的起始和结束点长度为N t0=fix(delaym/dt)+1; t1=fix((delaym+Tp)/dt); tm=[t0*dt-delaym:dt:t1*dt-delaym]-Tp/2; %点目标雷达回波 temp(t0:t1)=temp(t0:t1)+(tar(m,3)+cj*tar(m,4))*exp(cj*pi*K*tm.^2)... *exp(-cj*4*pi/lamda*sqrt(dazimuth^2+r^2)); end end sr(i,:)=temp; % fwrite(fid,[real(temp),imag(temp)],'float32');%按时部虚部进行文件存储 Max_Echo(i)=max(abs(temp)); waitbar(i/rawdatawidth); end close(Hwaitbar); % fclose(fid); figure;imagesc(abs(sr)); sr = sr.'; save sarecho.mat Head sr azm; %保存回波和关键参数