Shift-invariant double-foundation foresight synthetic aperture radar NLCS imaging method

Abstract

The invention discloses a shift-invariant double-foundation foresight synthetic aperture radar NLCS imaging method. Specifically, quartic smoothing and range four-order nonlinear Chirp-Scaling are combined, and the problems of nonlinear space variation of shift-invariant double-foundation foresight SAR range migration (RCM) along with a range and linear space variation of quadratic range compression (SRC) along with the range are solved. The shift-invariant double-foundation foresight synthetic aperture radar NLCS imaging method is characterized in that firstly, echo is subjected to quartic smoothing in a two-dimensional frequency domain, so that the two-dimensional degree of freedom is increased; secondly, range four-order nonlinear Chirp-Scaling operation is performed in a direction frequency domain distance time domain, so that the nonlinear space variation of the RCM along with the range and the linear space variation of the SRC along with the range are eliminated; accurate correction of the shift-invariant double-foundation foresight SAR range migration and removal of the space variation of the SRC can be realized, and accurate focusing of a double-foundation foresight SAR is completed.

Description

technical field [0001] The invention belongs to the field of radar technology, and in particular relates to a shift-invariant bistatic forward-looking SAR imaging method in synthetic aperture radar imaging technology. Background technique [0002] Synthetic Aperture Radar (SAR) is an all-weather, all-weather modern high-resolution microwave remote sensing imaging radar, which uses the relative motion between the radar antenna and the target area to obtain high spatial resolution. Synthetic aperture radar has played an increasingly important role in the fields of terrain surveying and mapping, vegetation analysis, ocean and hydrological observation, environment and disaster monitoring, resource exploration, and detection of small changes in the earth's crust. However, due to the limitation of its own working system, the existing single-base SAR cannot realize high-resolution imaging of the forward-looking area of ​​the aircraft, so that the SAR technology cannot fully play it...

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Problems solved by technology

[0005] In the literature "R.K.Raney, H.Runge, R.Bamler, I.G.Cumming, and F.H.Wong: Precision SAR processing using chirp scaling, IEEE Trans.Geosci.Remote Sens., vol.32, no.4, pp.786-799 , Jul.1994", the traditional Chirp-Scaling (CS) method was applied to BFSAR imaging processing, but the linear Chirp-Scaling method ignored the space variation of the quadratic range compression, and in BFSAR, the distance Migration along the distance has the characteristics of nonlinear space variation, which will directly affect the final imaging effect

[0006] In the literature "X.Qiu, D.Hu, and C.Ding: Some reflections on bistatic SAR of forward-looking configuration, IEEE Geosci.Remote Sens. Lett., vol.5, no.4, pp.735-739, 2008", the range-Doppler method was applied to BFSAR imaging processing, but this method did not consider the spatial variability of SRC, and in BFSAR, SRC has a large linear spatial variability along the range direction, which will directly affect the final Imaging effect

[0007] In the literature "Z. Hua and L. Xingzhao: An Extended Nonlinear Chirp-Scaling Algorithm for Focusing Large-Baseline Azimuth-Invariant Bistatic SAR Data, IEEE Geosci. Remote Sens. Lett., vol.6, no.3, pp.548 -552, 2009", the nonlinear CS method is applied, but the problem of linear space variation of SRC along the distance direction in BFSAR is also ignored

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