echoback.m

进行ISAR运动补偿的程序 kylsdone 方法来消除越距离单元走动,注释完整

function z=echoback(rho,theta,model);

% function z = ECHOBACK(rho,theta,model)
% z     : echo return matrix (saved in ZDATA.MAT)
% rho   : matrix of data frequencies
% theta : matrix of data angles
% model : target point model, composed by three rows:
%         model(1,:) = positions in X 
%         model(2,:) = positions in Y 
%         model(3,:) = amplitudes in linear scale
% model has to be changed according its postion and
% amplitude.
%

xp=model(1,:); yp=model(2,:);
ap=model(3,:); ap = ap./max(ap); 
rhop=sqrt(xp.^2+yp.^2); thetap=atan2(yp,xp); 

%%% Echo return signal generation
z=zeros(size(rho));
for times = 1:length(xp),
thetaz = thetap(times) + theta;
phi = (4 * pi * rhop(times) / 3e8) .* rho .* cos(thetaz);
z = z + ap(times) .* exp(j .* phi); end

save zdata z

w=(hamming(size(rho,1))*hamming(size(rho,2))');
s=fftshift(abs(fft2(flipud(z).*w,128,128)));
s=20.*log10(s./max(max(s)));
for a=1:size(s,1);for b=1:size(s,2),
if s(a,b)<-40,s(a,b)=-40;end;end;end
image(s+40)
colormap('gray')
axis('image')
%ss=fftshift(abs(fft2(flipud(z))));
%image(ss)
%colormap('gray')
%axis('image')