Imaging synthetic aperture radar

Patent · Tue Dec 31 23:00:00 EST 1996

OSTI ID:870851

Burns, Bryan L ^[1]; Cordaro, J Thomas ^[2]

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1. Tijeras, NM
2. Albuquerque, NM

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 integrated 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.

• Research Organization: Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA
• Assignee: United States of America as represented by United States (Washington, DC)
• Patent Number(s): US 5608404
• OSTI ID: 870851
• Country of Publication: United States
• Language: English

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