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AssigneeThe United States of America as represented by the Administrator of the National Aeronautics and Space Administration
InventorsChialin Wu, Kuang Y. Liu
Estimating the term…
A synthetic aperture radar system (SAR) having a range correlator (10) is provided with a hybrid azimuth correlator (12) for correlation utilizing a block-pipelined Fast Fourier Transform (12a) having a predetermined FFT transform size with delay elements (Z) for so delaying SAR range correlated data as to embed in the Fourier transform operation a corner-turning function as the range correlated SAR data is converted from the time domain to a frequency domain. A transversal filter (12b) connected to receive the SAR data in the frequency domain, and from a generator (14b) a range migration compensation function, D, to a programmable shift register (30) for accurate range migration compensation; weights, W.sub.i, to multipliers (35-38) for interpolation, and an azimuth reference function, .phi..sub.j, in the frequency domain to a multiplier 42 for correlation of the SAR data. Following the transversal filter is a block-pipelined inverse FFT (12c) used to restore azimuth correlated data in the frequency domain to the time domain for imaging. The FFT transform size is selected to accommodate the different SAR azimuth aperture lengths, number of looks and prefiltering requirements.
In a synthetic aperture radar system (SAR) having means for correlating range sampled data with a range reference function to produce the SAR response of range correlated data in sequential form, range line by range line in the time domain, a method for correlating said SAR response in the azimuth direction utilizing a block-pipelined Fast Fourier Transform (FFT) operation with a predetermined FFT transform size comprised of the step of delaying said SAR response to embed in the Fourier transform operation a corner-turning function as said SAR response is converted from the time domain to a frequency domain, providing predetermined delays for said SAR response for accurate range migration compensation and multiplying said SAR response in the frequency domain with an azimuth reference function in the azimuth frequency domain.
In a synthetic aperture radar system (SAR) having means for correlating range sampled data with a range reference function to produce the SAR response of range correlated data in sequential form, range line by range line in the time domain, apparatus for correlating said SAR response in the azimuth direction utilizing a block-pipelined Fast Fourier Transform (FFT) having a predetermined FFT transform size comprised of means for delaying said SAR response to embed in the Fourier transform operation a corner-turning function as said SAR response is converted from the time domain to a frequency domain, and including a transversal filter connected to receive said SAR response in the frequency domain, said transversal filter having means for accurate range migration compensation and means for multiplying said SAR response in the frequency domain with an azimuth reference function in the azimuth frequency domain.
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