matlab 合成孔径雷达(SAR)的点目标仿真.zip

%%================================================================ %%Filename: stripmapSAR.m %%Help file: stripmapSAR.doc %%Project: Stripmap SAR Simulation using point targets and Reconstrction %%================================================================ clear;clc;close all; %%================================================================ %%Parameter--constant C=3e8; %propagation speed %%Parameter--radar characteristics Fc=1e9; %carrier frequency 1GHz lambda=C/Fc; %wavelength %%Parameter--target area Xmin=0; %target area in azimuth is within[Xmin,Xmax] Xmax=50; Yc=10000; %center of imaged area Y0=500; %target area in range is within[Yc-Y0,Yc+Y0] %imaged width 2*Y0 %%Parameter--orbital information V=100; %SAR velosity 100 m/s H=5000; %height 5000 m R0=sqrt(Yc^2+H^2); %%Parameter--antenna D=4; %antenna length in azimuth direction Lsar=lambda*R0/D; %SAR integration length Tsar=Lsar/V; %SAR integration time %%Parameter--slow-time domain Ka=-2*V^2/lambda/R0; %doppler frequency modulation rate Ba=abs(Ka*Tsar); %doppler frequency modulation bandwidth PRF=Ba; %pulse repitition frequency PRT=1/PRF; %pulse repitition time ds=PRT; %sample spacing in slow-time domain Nslow=ceil((Xmax-Xmin+Lsar)/V/ds); %sample number in slow-time domain Nslow=2^nextpow2(Nslow); %for fft sn=linspace((Xmin-Lsar/2)/V,(Xmax+Lsar/2)/V,Nslow);%discrete time array in slow-time domain PRT=(Xmax-Xmin+Lsar)/V/Nslow; %refresh PRF=1/PRT; ds=PRT; %%Parameter--fast-time domain Tr=5e-6; %pulse duration 10us Br=30e6; %chirp frequency modulation bandwidth 30MHz Kr=Br/Tr; %chirp slope Fsr=3*Br; %sampling frequency in fast-time domain dt=1/Fsr; %sample spacing in fast-time domain Rmin=sqrt((Yc-Y0)^2+H^2); Rmax=sqrt((Yc+Y0)^2+H^2+(Lsar/2)^2); %SAR正对目标，所以与æœ?¿œå¤„的距离为合成孔径长度的ä¸?Š Nfast=ceil(2*(Rmax-Rmin)/C/dt+Tr/dt);%sample number in fast-time domain Nfast=2^nextpow2(Nfast); %for fft tm=linspace(2*Rmin/C,2*Rmax/C+Tr,Nfast); %discrete time array in fast-time domain dt=(2*Rmax/C+Tr-2*Rmin/C)/Nfast; %refresh Fsr=1/dt; %%Parameter--resolution DY=C/2/Br; %range resolution DX=D/2; %cross-range resolution %%Parameter--point targets Ntarget=1; %number of targets %format [x, y, reflectivity] Ptarget=[Xmin,Yc,1]; disp('Parameters:') disp('Sampling Rate in fast-time domain');disp(Fsr/Br) disp('Sampling Number in fast-time domain');disp(Nfast) disp('Sampling Rate in slow-time domain');disp(PRF/Ba) disp('Sampling Number in slow-time domain');disp(Nslow) disp('Range Resolution');disp(DY) disp('Cross-range Resolution');disp(DX) disp('SAR integration length');disp(Lsar) disp('Position of targets');disp(Ptarget) %%================================================================ %%Generate the raw signal data K=Ntarget; %number of targets N=Nslow; %number of vector in slow-time domain M=Nfast; %number of vector in fast-time domain T=Ptarget; %position of targets Srnm=zeros(N,M); for k=1:1:K sigma=T(k,3); Dslow=sn*V-T(k,1); R=sqrt(Dslow.^2+T(k,2)^2+H^2); tau=2*R/C; Dfast=ones(N,1)*tm-tau'*ones(1,M); phase=pi*Kr*Dfast.^2-(4*pi/lambda)*(R'*ones(1,M)); Srnm=Srnm+sigma*exp(j*phase).*(0<Dfast&Dfast<Tr).*((abs(Dslow)<Lsar/2)'*ones(1,M)); end %%================================================================ %%Range compression tr=tm-2*Rmin/C; Refr=exp(j*pi*Kr*tr.^2).*(0<tr&tr<Tr); Sr=ifty(fty(Srnm).*(ones(N,1)*conj(fty(Refr)))); Gr=abs(Sr); %%Azimuth compression ta=sn-Xmin/V; Refa=exp(j*pi*Ka*ta.^2).*(abs(ta)<Tsar/2); Sa=iftx(ftx(Sr).*(conj(ftx(Refa)).'*ones(1,M))); Ga=abs(Sa); %%================================================================ %%graw the intensity image of signal colormap(gray); figure(1) subplot(211); row=tm*C/2-2008;col=sn*V-26; imagesc(row,col,255-Gr); %intensity image of Sr axis([Yc-Y0,Yc+Y0,Xmin-Lsar/2,Xmax+Lsar/2]); xlabel('\rightarrow\itRange in meters'),ylabel('\itAzimuth in meters\leftarrow'), title('Stripmap SAR after range compression'), subplot(212); imagesc(row,col,255-Ga); %intensity image of Sa axis([Yc-Y0,Yc+Y0,Xmin-Lsar/2,Xmax+Lsar/2]); xlabel('\rightarrow\itRange in meters'),ylabel('\itAzimuth in meters\leftarrow'), title('Stripmap SAR after range and azimuth compression'), %%================================================================ %%draw 3D picture figure(2) waterfall(real(Srnm((200:205),:)));axis tight xlabel('Range'),ylabel('Azimuth'), title('Real part of the raw signal'), figure(3) waterfall(Gr((200:205),(600:1000)));axis tight xlabel('Range'),ylabel('Azimuth'), title('Stripmap SAR after range compression'), figure(4) mesh(Ga((200:300),(750:860)));axis tight xlabel('Range'),ylabel('Azimuth'), title('Stripmap SAR after range and azimuth compression'), %%================================================================ %%draw -3dB contour figure(5) a=max(max(Ga)); contour(row,col,Ga,[0.707*a,a],'b');grid on axis([9995,10050,-20,20]), xlabel('\rightarrow\itRange in meters'),ylabel('\itAzimuth in meters\leftarrow'), title('Resolution Demo: -3dB contour'); %%================================================================