Imaging for High-Resolution Resolution Wide Wide-Swath Swath Spaceborne SAR Using Cubic Filtering and NUFFT Based on Circular Orbit Approximation
Abstract: In the processing of high-resolution resolution wide wide-swath spaceborne synthetic aperture radar data, the slant range history is difficult to formulate with a high accuracy over a long data-acquisition acquisition interval, and the variation of the imaging parameters over the illuminated scene makes it necessary to implement 22-D D space-variant space processing. To deal with these issues, first, a slant range expression is derived based on a geometry model using a circular arc to approximate the curved trajectory in this paper, which is composed of a hyperbolic term, a cubic term, and a quartic term. Then, the imaging flow based on the slant range model is proposed: a cubic filtering in range is employed to normalize the range-variant range secondary range compression; the nonuniform fast Fourier transform (NUFFT) is used to correct the additional rang range e displacement introduced by the cubic filtering and the nonlinear range cell migration (RCM) caused by the range dependence of the velocity; necessary modifications are made on the matched filter for azimuth compression to accommodate the cubic filtering in range and to deal with the high-order order terms of the slant range model. The simulation results show that the proposed slant range model has a relatively high accuracy; the range processing procedure that involves an NUFFT following a cubic filtering can apply pply to the case where the nonlinear chirp scaling algorithm is adopted, and it has the advantage of being capable of dealing with the nonlinear RCM; the