Abstract
Maneuvers provide flexibility for high-resolution highly-squinted (HRHS) airborne synthetic aperture radar (SAR) imaging and also mean complex signal properties in the echoes. In this paper, considering the curved path described by the fifth-order motion parameter model, effects of the third- and higher-order motion parameters on imaging are analyzed. The results indicate that the spatial variations distributed in range, azimuth, and height directions, have great impacts on imaging qualities, and they should be eliminated when designing the focusing approach. In order to deal with this problem, the spatial variations are decomposed into three main parts: range, azimuth, and cross-coupling terms. The cross-coupling variations are corrected by polynomial phase filter, whereas the range and azimuth terms are removed via Stolt mapping. Different from the traditional focusing methods, the cross-coupling variations can be removed greatly by the proposed approach. Implementation considerations are also included. Simulation results prove the effectiveness of the proposed approach.
Highlights
In recent years, there have been tremendous studies on synthetic aperture radar (SAR)
The maneuvers will greatly affect the spatial variations in both the range and azimuth directions, for the high-resolution highly-squinted (HRHS) SAR
Our analyses suggest that the spatial variations in arbitrary direction brought by the third- and higher-order motion parameters cannot be ignored
Summary
There have been tremendous studies on synthetic aperture radar (SAR). The maneuvers will greatly affect the spatial variations in both the range and azimuth directions, for the high-resolution highly-squinted (HRHS) SAR. Compared with the conventional HRM, these models introduce acceleration into the range model, which makes the descriptions of characteristics, including Doppler bandwidth, cross-coupling phase, and two-dimensional (2-D) spatial variations, of the raw-data more accurate They only consider the acceleration term and ignore the higher-order motion parameters, which limit their applications for high-accuracy imaging. The maneuvers cannot always be controlled only by constant velocity and acceleration, the higher-order motion parameters are needed [18] If this problem cannot be well solved, it may strongly impair the final image quality in terms of geometric distortion and radiometric resolution losses for HRHS SAR [5].
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