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TitleAdaptive Compensation of RADARSAT SAR Analoque-to-Digital Converter Saturation Power Loss
DownloadDownloads (Preprint)
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorVachon, P W; Gray, A L; Livingstone, C; Luscombe, A P
SourceInternational Symposium, Geomatics in the Era of RADARSAT (GER'97), Ottawa, Canada, May 25-30; 1997., Open Access
logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20041957
Mediapaper; on-line; digital
File formatpdf
Released1997 01 01
AbstractDark rangeward bands sometimes appear in RADARSAT synthetic aperture radar (SAR) imagery of the coastal zone. These bands may be visible over land or ice when water is in the near range. This artifact arises since RADARSAT's automatic gain control (AGC) is set by the near-half swath alone, while the far-half swath could return more power than the near-half swath, depending on scene content. If the gain is inappropriately set too high for the far-half swath, then the radar's 4-bit analogue-to-digital converter (ADC) will saturate, one effect of which is a loss in power and the appearance of the image banding. We havetested a simple correction methodology to improve image radiometry under these circumstances. Based upon measurement of the signal data variance and the power loss properties of a 4-bit ADC, an adaptive gain parameter is estimated which is used to scale the signal data and recover the lost power. As the ADC saturation represents a real information loss, the dynamic range of the rescaled image is reduced in the saturated regions. The methodology has been implemented for our workstation-based SAR processor. We describe the correction methodology and present some algorithm test results.

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