Unified imaging method for synthetic aperture radar (SAR) in four modes

Abstract

The invention discloses a unified imaging method for a synthetic aperture radar (SAR) in four modes aiming at the strip SAR, bunching SAR, sliding bunching SAR and TOPS SAR. The problem that the prior art is limited by the modes of the SAR is mainly solved. The method comprises the implementation processes of (1) receiving echo data of the original SAR of a platform, and performing range Fourier transform on an echo signal; (2) performing fractional order Fourier transform twice on the echo signal, and performing direction scaling processing; (3) performing range migration correction on the echo signal, and compensating a phase curve into a straight line through a hyperbolic curve; and (4) performing the fractional order Fourier transform twice, realizing focusing imaging, and removing the residual phase. The SAR imaging in the four modes can be finished through simple parameter setting, different scene and resolution requirements can be met, and the imaging method is wide in application range and can be applied to the fields of ground mapping, target identification and the like.

Description

Technical field [0001] The invention belongs to the field of radar signal processing, and particularly relates to multi-mode SAR focusing, and can be used for airborne and spaceborne platform SAR imaging processing. Background technique [0002] Synthetic Aperture Radar SAR imaging is a high-resolution imaging technology. In the distance direction, it can obtain high resolution by transmitting a large bandwidth signal; in the azimuth direction, a moving sensor is used to simulate a long antenna array to obtain better resolution in this direction. rate. In the past half a century, SAR imaging theory and technology have developed greatly, and have been widely used, such as remote sensing and map surveying. [0003] So far, there are basically four commonly used SAR imaging modes, namely strip SAR mode, spotlight SAR mode, sliding spotlight SAR mode and TOPS SAR mode. The imaging processing algorithms of different modes are different, and the imaging of each mode is SAR. There has b...

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Problems solved by technology

However, these methods are not suitable for imaging of strip SAR or spotlight SAR

[0007] As another way of thinking, an improved method of "two-step processing" can also be applied to TOPS SAR and sliding spotlight SAR mode imaging, because the direct azimuth matching filtering or azimuth-to-baseband compression in this algorithm may cause azimuth Image aliasing, G.Engen proposed a mobile frequency band chirpz conversion method that does not use sub-aperture processing TOPS SAR data, Sun proposed a unified processing algorithm suitable for these two SAR data, although this method can avoid azimuth spectrum And the aliasing problem of azimuth images, but still not suitable for imaging processing of spotlight SAR or strip SAR

[0008] The above imaging processing algorithms are only for one or two SAR modes, but cannot take into account the four SAR modes at the same time

For different modes, it is necessary to install corresponding imaging processing modules on the carrier aircraft, which increases the research cost and brings a lot of inconvenience when the imaging scene is unknown

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