Translational motion compensation methods for inverse synthetic aperture radar imagery
In this dissertation, methods for estimating the kinematic parameters of a target from its stepped-frequency inverse synthetic aperture radar (ISAR) signature are developed, implemented, and tested. Kinematic parameters must be estimated and their effects compensated via focal quality indicators in order to generate focused ISAR imagery. The optimization of kinematic parameter estimation is a multiple dimensional search problem that minimizes the number of iterations needed to reach the absolute minimum of a focal quality indicator surface. ^ Image entropy is the traditional focal quality indicator for ISAR motion compensation. However, the image focusing process based on entropy measurements involves the two-dimensional Fourier transform, so the process is computationally intensive. ^ Alternative methods that use the phase of the target's echo transfer function to calculate a focal quality indicator while avoiding two-dimensional Fourier processing are proposed. The goal is to design focal quality indicators that yield optimum motion parameter estimates with the least number of computations so that a focused ISAR image is generated efficiently. ^ Complex analysis is introduced to measure the slope of the phase more accurately by selecting segments of the echo transfer function with high signal to noise ratio levels. A weighted least squares method is utilized to make the focal quality indicator more robust by assigning reliability weights to data segments with larger amplitude and longer lengths. ^ The Creamery bounds for the stepped frequency wavering. are derived and implemented in the context of weighted least squares complex analysis. The Creamery bounds for motion parameter estimation provide the lower limits for estimation accuracy. ^ Test results show. that the focal quality indicator designed using weighted least squares complex analysis yields the motion parameters with high accuracy and efficiency. ^
Engineering, Electronics and Electrical|Remote Sensing
Son, Jae Sok, "Translational motion compensation methods for inverse synthetic aperture radar imagery" (1999). ETD Collection for University of Texas, El Paso. AAI9937182.