Communications: directive radio wave systems and devices (e.g. – Synthetic aperture radar
Reexamination Certificate
2006-12-05
2006-12-05
Tarcza, Thomas H. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Synthetic aperture radar
C342S02500R, C342S02500R, C342S161000, C342S196000
Reexamination Certificate
active
07145496
ABSTRACT:
A radar on a moving platform generates an initial synthetic aperture (SAR) image of a scene from a sequence of periodic pulse returns approximately motion compensated. The SAR image is formed from pixel intensities zn(x,y) within a x,y extent of the initial synthetic aperture image. Targets are selected from the initial synthetic aperture image using a sliding window, computing a first entropy for the selected targets, and sorting the targets using the first entropy to obtain a target list having target elements, then concatenating the target elements to form a data matrix compatible in the azimuth dimension with a Fast Fourier Transform.A phase correction for autofocus is iteratively computed and applied to the initial synthetic aperture image using an inner loop, a mid loop and an outer loop. The phase correction is expressed using an orthogonal polynomial having a plurality n consecutive terms an, a2denoting a quadratic term, and aNdenoting a last order term. The outer loop, using an L index, calculates an outer loop EL(a2) entropy for the quadratic term and an outer loop EL(aN) entropy for the last order term. Iterations within the outer loop continue until EL(a2)−EL(aN) is less than an outer loop tolerance.Similarly, the mid loop, and inner loop continue until the computation of their respective entropies meet a pre-set tolerance. The inner loop entropy uses a Golden Section search for computing the inner loop entropy.
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Cho Kwang M.
Hui Leo H.
Alkov Leonard A.
Alsomiri Isam
Raytheon Company
Tarcza Thomas H.
Vick Karl A.
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