Browse Prior Art Database

Synthetic Aperture Radar Processing Algorithm

IP.com Disclosure Number: IPCOM000122469D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 83K

Publishing Venue

IBM

Related People

Turner, R: AUTHOR

Abstract

This article relates to the processing of raw Synthetic Aperture Radar (SAR) data to form an SAR image. It is applicable to the matched filtering, range-doppler SAR processing technique. The algorithm disclosed provides approximately a 30% reduction in the computation required, significant in view of the large (typically 10**10) number of floating-point operations required. The algorithm also maintains full resolution in the azimuth (along track) direction and reduces the memory and bandwidth requirements of an SAR processor.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Synthetic Aperture Radar Processing Algorithm

      This article relates to the processing of raw Synthetic
Aperture Radar (SAR) data to form an SAR image.  It is applicable to
the matched filtering, range-doppler SAR processing technique.  The
algorithm disclosed provides approximately a 30% reduction in the
computation required, significant in view of the large (typically
10**10) number of floating-point operations required.  The algorithm
also maintains full resolution in the azimuth (along track) direction
and reduces the memory and bandwidth requirements of an SAR
processor.

      Conventional filter, range-doppler approach to SAR processing
is prior art, involving several steps, in a fixed sequence:
1.   Range processing    a.   forward FFT of data
                         b.   convolve with matched filter
                         c.   correct for coarse linear error -
"range walk"
                         d.   inverse FFT of data
2.   Pre-summation (4 to 1)
3.   Corner turning
4.   Azimuth processing  a.   forward FFT of data
                         b.   convolve with matched filter
                         c.   correct for quadratic error - "range
curvature" and any residual non-linear range walk.
                         d.   inverse FFT of data
5.   Multilook processing (optional)

      The range processing step compresses the received radar pulses
and corrects for range walk, a linear error due to spacecraft motion.
Each azimuth line must be processed, requiring one forward and one
backward 4096-point FFT per line.  The next step is pre-summation,
where (in the case of ERS-1) four azimuth lines are averaged.  This
reduces the number of azimuth lines to 6750 which are then corner-
turned.  Finally, azimuth processing is performed.  This requires a
forward FFT, followed by matched filtering, and quadratic error
correction to compensate for errors such as antenna pointing errors.
The data is then inverse Fourier transformed.  Each FFT must have a
length that is a power of two, so two overlapping 4096-point FFTs are
used to process each azimuth line of length 6750.

      In the conventional algorithm, the range processing step is...