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Title: Imaging synthetic aperture radar

A linear-FM SAR imaging radar method and apparatus to produce a real-time image by first arranging the returned signals into a plurality of subaperture arrays, the columns of each subaperture array having samples of dechirped baseband pulses, and further including a processing of each subaperture array to obtain coarse-resolution in azimuth, then fine-resolution in range, and lastly, to combine the processed subapertures to obtain the final fine-resolution in azimuth. Greater efficiency is achieved because both the transmitted signal and a local oscillator signal mixed with the returned signal can be varied on a pulse-to-pulse basis as a function of radar motion. Moreover, a novel circuit can adjust the sampling location and the A/D sample rate of the combined dechirped baseband signal which greatly reduces processing time and hardware. The processing steps include implementing a window function, stabilizing either a central reference point and/or all other points of a subaperture with respect to doppler frequency and/or range as a function of radar motion, sorting and compressing the signals using a standard fourier transforms. The stabilization of each processing part is accomplished with vector multiplication using waveforms generated as a function of radar motion wherein these waveforms may be synthesized in integratedmore » circuits. Stabilization of range migration as a function of doppler frequency by simple vector multiplication is a particularly useful feature of the invention; as is stabilization of azimuth migration by correcting for spatially varying phase errors prior to the application of an autofocus process.« less
Authors:
 [1] ;  [2]
  1. (Tijeras, NM)
  2. (Albuquerque, NM)
Publication Date:
OSTI Identifier:
870851
Report Number(s):
US 5608404
DOE Contract Number:
AC04-76
Resource Type:
Patent
Research Org:
Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA
Country of Publication:
United States
Language:
English
Subject:
imaging; synthetic; aperture; radar; linear-fm; method; apparatus; produce; real-time; image; arranging; returned; signals; plurality; subaperture; arrays; columns; array; samples; dechirped; baseband; pulses; including; processing; obtain; coarse-resolution; azimuth; fine-resolution; range; lastly; combine; processed; subapertures; final; efficiency; achieved; transmitted; signal; local; oscillator; mixed; varied; pulse-to-pulse; basis; function; motion; moreover; novel; circuit; adjust; sampling; location; sample; rate; combined; greatly; reduces; time; hardware; steps; implementing; window; stabilizing; central; reference; respect; doppler; frequency; sorting; compressing; standard; fourier; transforms; stabilization; accomplished; vector; multiplication; waveforms; generated; synthesized; integrated; circuits; migration; simple; particularly; useful; feature; correcting; spatially; varying; phase; errors; prior; application; autofocus; process; radar motion; greatly reduces; aperture radar; phase error; processing time; particularly useful; integrated circuits; integrated circuit; fourier transform; processing steps; synthetic aperture; local oscillator; varying phase; processing step; phase errors; oscillator signal; transmitted signal; doppler frequency; returned signal; subaperture array; greatly reduce; fourier transforms; imaging radar; aperture arrays; /342/