0.6 Appendix and references

Appendix

Matlab function for processing sar data

function img = sar_lin(f,az_lin,iq_lin)

% INITIALIZATION

R=4*pi*f/3e8;% Transformation of Time Freqeuncy to Spatial Frequency

A=pi/180*az_lin;% Transformation of Angle in degree to radians

for j=1:147

A(j)=A(j)-2*pi;% Adjustment so that all angular values are between 0 and pi

end

% Initialization of Cartesian Grid

X=zeros(1,175);

Y=zeros(175,1);

for j=1:175

X(j)=208+(j-1);

Y(j)=208+(j-1);

end

val=zeros(175);% Initialize the matrix of values in the cartesian grid.

% INTERPOLATOR

for j=1:175

j % Update on how far we are.

for k=1:175

r=sqrt(X(j)^2+Y(k)^2);

a=atan(Y(k)/X(k));

if (r>R(1)&r<R(512))

% Data index of cartesian point

J=ceil((r-R(1))*511/(R(512)-R(1)));

K=ceil((a-A(1))*1540/(A(1541)-A(1)));

% Linearly interpolate the cartesian point with its 4 nearest neighbor polar data points.

% Interpolate in R

v0 = 1/(R(J+1)-R(J)) * ( iq_lin(J,K)*(R(J+1)-r) + iq_lin(J+1,K)*(r-R(J)) );

v1 = 1/(R(J+1)-R(J)) * ( iq_lin(J,K+1)*(R(J+1)-r) + iq_lin(J+1,K+1)*(r-R(J)) );

% Interpolate in THETA

val(j,k) = 1/(A(K+1)-A(K)) * ( v0*(A(K+1)-a) + v1*(a-A(K)) );

end

end

end

% Plot the interpolated values

figure(1)

imagesc(abs(val));

% Take the 2d inverse DFT to get the image

img = ifft2(val);

% Plot the image

figure(2)

imagesc(abs(img));

References

D. C. Munson Jr., J. D. O’Brien, W. K. Jenkins, “A Tomographic Formulation of Spotlight-Mode Synthetic Aperture Radar,” Proc. IEEE, vol. 71, pp 917-925, August 1983.

D. C. Munson Jr., R. L. Visentin, “A Signal Processing View of Strip-Mapping Synthetic Aperture Radar,” IEEE Transactions on Acoustics, Speech, and Signal Processing, vol. 37, no. 12, pp 2131-2147, December 1989.

G. D. Martin, A. W. Doerry, “SAR Polar Format Implementation with MATLAB,” Sandia National Laboratories, SAND2005-7413, November 2005.

P. Buxa, L. Gorham, Lt. M. Lukacs, “Mapping of a 2D SAR Backprojection Algorithm to an SRC Reconfigurable Computing MAP Processor,” Air Force Research Laboratory, Sensors Directorate.