Motion measurement errors analysis for the “one-active” LASAR
The influences of the motion measurement errors (MMEs) to the 3D SAR imaging are analyzed based on the “one-active” LASAR system in this paper. Firstly, the principle and the spatial ambiguity function (AF) of the “one-active” LASAR are introduced. Then the 3D MMEs are introduced according to three forms: the 3D velocity errors and the 3D acceleration errors, the sine vibration errors and the array vibration errors. The 3D SAR system's maximum allowable MMEs are obtained and the influences of the 3D MMEs to the 3D AF are analyzed by the numerical simulation. Finally, the ground experiments and its results are presented, which validate the feasibility of the “one-active” LASAR.
Motion measurement errors and autofocus in bistatic SAR
This paper discusses the effect of motion measurement errors (MMEs) on measured bistatic synthetic aperture radar (SAR) phase history data that has been motion compensated to the scene origin. We characterize the effect of low-frequency MMEs on bistatic SAR images, and, based on this characterization, we derive limits on the allowable MMEs to be used as system specifications. Finally, we demonstrate that proper orientation of a bistatic SAR image during the image formation process allows application of monostatic SAR autofocus algorithms in postprocessing to mitigate image defocus.
Some methods for reducing propagation-induced phase errors in coherent imaging systems. I - Formalism. II - Numerical results
The random phase errors induced in an electromagnetic wave propagating through turbulence in the troposphere and/or the ionosphere can degrade the performance of a coherent imaging system such as a synthetic-aperture radar. Several methods for removing or reducing these phase errors are described. Some of these methods, such as cubic-spline approximations with map drift and a deterministic technique based on a Legendre-series expansion of the phase error, are not new but are included for comparison. At least three techniques are (to our knowledge) new; a binary multiplexing scheme, a method using the Wigner–Ville distribution, and an optimal estimator based on the covariance matrix of the Legendre-series expansion coefficients. The method based on the Wigner–Ville distribution promises to be the most effective in reducing the deleterious effects of the phase errors on image quality.