SAR成像仿真Matlab程序-

1、clear all; %= % (I parameters' definition %= c=3e+8; % speed of light pi=3.1415926; % pi j00=sqrt(-1; % square root of -1 res_a=1; % required azimuth resolution res_r=1; % required range resolution k_a=1.2; % azimuth factor k_r=1.2; % range factor Ra=4000.; % radar working distance va=76.; % rad

2、ar/platform forward velocity Tp=1.e-6; % transmitted pulse width fc=3e+9; % carrier frequency FsFactor = 1.2; theta=90*pi/180; % squint angle %= lamda=c/fc; % wavelength Br=k_r*c/2./res_r; % required transmitted bandwidth Fs=Br*FsFactor; % A/D sampling rate bin_r=c/2./Fs; % range bin Kr=Br/Tp; % ran

3、ge chirp rate La=Ra*k_a*lamda/2/res_a/sin(theta; % required synthetic aperture length Ta=La/va;% required synthetic aperture time fdc=2*va*cos(theta/lamda; % doppler centriod fdr=-2*(va*sin(theta.2/lamda/Ra;% doppler rate Bd=abs(fdr*Ta;% doppler bandwidth prf=round(Bd*2; % PRF %= %(II echo return mo

4、delling (point target %= Na=fix(Ta*prf; % azimuth sampling number ta=(1:Na-Na/2/prf; % slow time along azimuth xa=va*ta-Ra*cos(theta; % azimuth location along flight track %x0= 0 0 0 0 0 ; % define multi points if you want %R0=-20 -10 0 10 20 ; % x0: azimuth location (positive towards forward veloci

5、ty % R0: slant range location (positive towards far range x0= 0 0 0 50; R0= -200 -50 0 0; Npt_num = length(x0; ra=zeros(Npt_num, length(xa; % calculate every point target's slant range history for i=1:Npt_num ra(i,=sqrt(Ra*sin(theta+R0(i.2+(xa+x0(i.2; end rmax=max(max(ra; % max. slant range rmin

6、=min(min(ra; % min. slant range rmc=fix(rmax-rmin/bin_r;% range sample number rg=0*ra; % initialize rg=fix(ra-rmin/bin_r+1; % range gate index rgmax=max(max(rg; rgmin=min(min(rg; nr=round(Tp*Fs; % samples of a pluse tr=1:fix(nr+1; tr=tr/Fs-Tp/2; % fast time within a pluse duration Nr=nr+rgmax; %= %(

7、II echo return modelling (point target %= sig=zeros(Na,Nr; for i=1:Na for k=1:Npt_num sig(i,rg(k,i:rg(k,i+nr=sig(i,rg(k,i:rg(k,i+nr+exp(-j00*4*pi/lamda*ra(k,i*exp(-j00*pi*Kr*(tr.2; end end %= % Range Doppler Algorithm %= pre_filter=exp(-j00*2*pi*fdc*ta' for i=1:Nr sig(:,i=sig(:,i.*pre_filter; en

8、d disp('end of prefilter' for i=1:Na sig(i,=fftshift(fft(sig(i,; end dfr=Fs/Nr; fr=(0:Nr-1-Nr/2*dfr; phase1=exp(-j00*pi*(fr.2/Kr; for i=1:Na sig(i,=ifft(fftshift( sig(i,.*phase1 ; end disp('end of range compression' figure; colormap(gray; contour(abs(sig; %= for i=1:Nr sig(:,i=fftshi

9、ft(fft(sig(:,i; end disp('end of azimuth fft' dfa=prf/Na; fa=(0:Na-1-Na/2*dfa+fdc; figure;colormap(gray; contour(abs(sig; % RMC with interpolation rr=rmin+(1:Nr-1*bin_r; R=8; N_ex=2000; Up00=zeros(size(1:Nr*R+2*N_ex; alpha_dc=1./sqrt(1-(lamda*fdc/2/va2; for i=1:Na Up00=0*Up00; Up00(N_ex+1:N_

10、ex+Nr*R=interp(sig(i,R; alpha_fx = 1./sqrt(1-(lamda*fa(i/2/va2; dRa=rr*(alpha_fx-alpha_dc*sin(theta; kpos=R*(1:Nr-1+round(R*dRa/bin_r+N_ex; sig(i,=Up00(kpos; end disp('end of range motion correction' figure; colormap(gray; contour(abs(sig; %= fa=fa-fdc; fdc=0; beta_dc = sqrt(1-(lamda*fdc/2/va.2; delt_beta = sqrt(1-(lamda*fa/2/va.2-beta_dc; phase2 = exp(j00*4*pi*sin(theta/lamda*(del