A novel modified Omega-K algorithm for circular trajectory scanning SAR imaging using series reversion

Abstract

This article presents a modified Omega-K algorithm for circular trajectory scanning synthetic aperture radar (CTSSAR) imaging. Due to the curvature of circular trajectory, it is difficult to have access to the two-dimensional frequency spectrum for CTSSAR via the principle of stationary phase (POSP), as conventional SAR imaging methods RD and CS. Herein, the analytic point target spectrum is first derived by series reversion and the POSP, based on which a modified Omega-K algorithm is developed to focus data accurately. The accuracy can be controlled by keeping enough terms in the two series expansions so that a well-focused image can be achieved with a proper range approximation. After detailed analyses and experiments, the fourth-order approximation is proved to be the best choice. Furthermore, the computational efficiency is evaluated by comparing the given method with the back projection algorithm and other methods with different approximated orders. The proposed algorithm is verified to be the best one in terms of computational burden. A well-focused image is obtained by simulations, validating the feasibility of the proposed algorithm.

Motion Error Compensation for Quad-rotor Miniature Unmanned Aerial Vehicle SAR Imaging

“…In this case, the range history R i (t) becomes R i (t) + ∆R i (t), and an additional phase modulation will be in S (k,t). The error ∆R i (t) will cause the SAR image degradation, such as smearing and deformation (Huang et al, 2011;Bao et al, 2012;Liao et al, 2013).…”

Analysis on parameters and imaging algorithm of squint circular trace scanning SAR

“…When it comes to the imaging processing, the azimuth segmentation precedes the imaging operation as shown in [5]. And the received echo signal is converted into 2D domain to compensate the high order errors then.…”

“…Circular trace scanning synthetic aperture radar (CTSSAR) is a specific kind of CSAR, with its beam fixed illuminating towards outside the circular cruising path [5]. The azimuth scanning velocity is then increased accordingly by its circular flight trajectory, leading to a larger observing area in a short time, which is an advantage superior to the traditional stripmap mode.…”

Modulus Stretch-Based Circular SAR Imaging with Contour Thinning

“…Liao et al presented a modified Omega-K algorithm to focus accurately. The accuracy can be controlled by keeping enough terms in the two series expansions so that a well-focused image can be achieved with a proper range approximation [22,23]. Li et al investigated the availability of an expediting backprojection algorithm for CSAR imaging.…”