NLCS Imaging Method for Shift-invariant Bistatic Forward-Looking Synthetic Aperture Radar

Abstract

The invention discloses a shift-invariant bistatic forward-looking synthetic aperture radar (NLCS) imaging method, which specifically combines four-time filtering and range-to-fourth-order nonlinear Chirp-Scaling to solve the problem of shift-invariant bistatic forward-looking SAR distance migration. Nonlinear space-variation of motion (RCM) with distance and linear space-variation of quadratic range compression (SRC) with distance. The characteristics of the method of the present invention: firstly, the echo is filtered four times in the two-dimensional frequency domain, which increases the two-dimensional degree of freedom; secondly, the distance to the fourth-order nonlinear Chirp-Scaling operation is performed in the azimuth frequency domain and the time domain, thereby eliminating The nonlinear space variation of RCM with range and the linear space variation of SRC with range can realize the accurate correction of range migration of bistatic forward-looking SAR and the removal of SRC space variation, and complete the accurate bistatic forward-looking SAR. focus.

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 chirpscaling, IEEE Trans. Geosci. RemoteSens., vol.32, no.4, pp.786-799, Jul.1994" In , the traditional Chirp-Scaling (CS) method is applied to image processing of BFSAR, but the linear Chirp-Scaling method ignores the space variation of the quadratic range compression, while in BFSAR, the range migration along the distance The direction 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 SARoffforward-looking configuration, IEEEGeosci.RemoteSens.Lett., vol.5, no.4, pp.735-739, 2008", range Doppler is applied The method performs imaging processing on BFSAR, but this method does not consider the spatial variability of SRC, and in BFSAR, SRC has a large linear spatial variability along the distance direction, which will directly affect the final imaging effect

[0007] In the literature "Z.HuaandL.Xingzhao: AnExtendedNonlinearChirp-ScalingAlgorithmforFocusingLarge-BaselineAzimuth-InvariantBistaticSARData, IEEEGeosci.RemoteSens.Lett., vol.6, no.3, pp.548-552, 2009", the nonlinear CS method is applied, but Also ignores the problem of linear space variation of SRC along the distance in BFSAR

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