Patent ID: 6781541
Filing Date: 2004-08-24
Classification: G01S

Abstract:
A radar system for acquiring synthetic aperture images of stationary targets, said radar system located on a moving platform, said moving platform moving in an along track direction, said along track direction perpendicular to a cross track direction, said radar system comprising:an analog to digital converter for converting a plurality of radar signals reflected from stationary targets located on a ground patch into digital values; memory for storing said digital values; motion compensation means for aligning said digital values stored within said memory along a motion compensation line to a first approximation of motion of said moving platform to generate motion compensated digital values; Fourier transform means for the conversion of said motion compensated digital values in said along track direction to a frequency domain; match filter function means to generate range compressed data for said stationary targets on said motion compensation line within said frequency domain; a Stolt interpolator for interpolating said range compressed data to generate interpolated values; means for skewing said interpolated values to reorient distortions arising from said first approximation of motion thereby generating an image data, said image data descriptive of said stationary targets in a range direction and an azimuth direction, said azimuth direction generally in said cross track direction; means for dividing said image data into overlapping sub-patches, each sub-patch containing a portion of said image data and overlapping data, said overlapping data part of said image data and common between two or more of said overlapping sub-patches; means for focusing each of said overlapping sub-patches individually using autofocus means to obtain focused sub-patches having a phase; means for adjusting said phase of each of said focused sub-patches to obtain a continuous phase with respect to one or more of said focused sub-patches, thereby obtaining smooth phase transition sub-patches; means for extracting said synthetic aperture images of stationary targets after concatenating said smooth phase transition sub-patches.