Ambiguities in target motion estimation for general SAR measurements

The article of record as published may be found at http://dx.doi.org/10.1049/iet-rsn.2016.0024This study investigates the ability to invert synthetic aperture radar (SAR) measurement data in order to obtain unique estimates of the underlying motion parameters of targets within the imaged scene. In particular, this investigation reveals that ambiguities exist in estimating the kinematics parameters of surface targets for cases of general bistatic SAR collections. Specifically, the current study presents a detailed methodology for constructing any number of alternate target trajectories which yield the same set of SAR measurements as that corresponding to the true target motion. Additionally, the target trajectory ambiguities of the current investigation are shown to remain even if the radar system obtains bistatic range-rate or Doppler measurements. Unambiguous kinematics estimates can be obtained only through additional constraints, as with assumptions that a given surface target lies on the one-dimensional locus of a road. Thus, the ability to localise and estimate unambiguous target motion parameters relies on the energy intensity patterns of the transmission and reception beams of the radar system. Overall, the current analysis provides a simple, and yet powerful, exposition of the nature of target trajectory ambiguities in monostatic and bistatic SAR imagery.AFR