Location
University of Utah
Start Date
6-19-1998 3:15 PM
Description
The Phase Gradient Autofocus algorithm (PG A) is widely used in spotlight mode SAR for motion compensation. The PG A algorithm has been proven to be a superior autofocus method. The original development needed high signal-to-scatter ratios. An improvement was made easing that restriction, but the narrow beam assumption (range dependent errors) remained. This paper progresses one step further by eliminating the narrow beam assumption. Lower altitude SARs have large range dependencies that cannot be ignored. A new phase estimator for PGA is introduced and extended to allow range dependence. An ERS-1 image of Death Valley is used in simulations comparing the new estimator to the maximum likelihood approach and in demonstrating the range-dependent PGA algorithm. Future approaches to the problem of strip-map SAR are also introduced.
Expansions and Discussions of the Phase Gradient Algorithm
University of Utah
The Phase Gradient Autofocus algorithm (PG A) is widely used in spotlight mode SAR for motion compensation. The PG A algorithm has been proven to be a superior autofocus method. The original development needed high signal-to-scatter ratios. An improvement was made easing that restriction, but the narrow beam assumption (range dependent errors) remained. This paper progresses one step further by eliminating the narrow beam assumption. Lower altitude SARs have large range dependencies that cannot be ignored. A new phase estimator for PGA is introduced and extended to allow range dependence. An ERS-1 image of Death Valley is used in simulations comparing the new estimator to the maximum likelihood approach and in demonstrating the range-dependent PGA algorithm. Future approaches to the problem of strip-map SAR are also introduced.