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AN ARCHITECTURE FOR FAST SAR PROCESSING 
Thilo Wolff 
European Space Operations Centre (ESOC)* 
Abstract 
Synthetic Aperture Radar (SAR) digital signal processing requires 
matched filtering for both range and azimuth compression. In contrast to 
the conventional fast convolution techniques a time domain matched 
filtering architecture is proposed here which is based on dedicated 
hardware and uses special VLSI processors in parallel. The advantage of 
the proposed azimuth compression concept is a continuous processing flow 
not artificially partitioned due to FFT size restrictions. 
The architecture covers the general case of range cell migration correc- 
tion and it avoids the so-called corner turning. 
1. Introduction 
  
Synthetic Aperture Radar (SAR) achieves high resolution imagery by pulse 
compression in range direction and with an effective long antenna - the 
synthetic aperture - along track (azimuth) direction by means of signal 
processing. The radar pulses emitted regularly are linearly frequency 
modulated and sampled radar echoes are subject to a Doppler shift which 
at first order causes also a linear frequency modulation. SAR image for- 
mation then in principle can apply a two dimensional matched filtering 
process. However, supposing that the Doppler phase shifts are several 
orders of magnitude smaller than the pulse frequency modulation the SAR 
signal processing can be separated into the range compression part and 
the azimuth compression part. 
If the SAR echoes are recorded digitally as it is usual today, the 
matched filtering results in convolution operations which can conven- 
iently be performed with powerful computers, but it still remains a 
demanding digital signal processing task. 
2. Digital SAR Processing 
  
2.1 Principal Steps and Difficulties 
  
  
Digital SAR processing comprises the following principal computational 
steps: 
- Preparation of processing parameters, 
- Range compression matched filtering, 
- Range cell migration correction (RCMC), 
- Azimuth compression matched filtering, 
- Image detection, and possibly re-mapping. 
* Robert-Bosch-Strasse 5, D-6100 DARMSTADT, Federal Republic of Germany. 
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