SAR (synthetic aperture radar) direction ambiguity suppression method based on antenna main lobe dominance intensity constraint

Abstract

The invention discloses an SAR (synthetic aperture radar) direction ambiguity suppression method based on antenna main lobe dominance intensity constraint and relates to synthetic aperture radar image techniques. The method includes: determining an antenna main lobe energy dominance region according to distribution conditions of SAR direction ambiguity energy within a PRF (pulse repetition frequency) corresponding to an antenna directivity diagram; completing data imaging of the antenna main lobe energy dominance region; taking the amplitude relation between the imaging result and an original full-resolution image as a judgment condition to subject the original full-resolution SAR image to selective intensity constraint to realize direction ambiguity suppression of the original image. The method overcomes the defect that traditional suppression methods are limited by scenes and target characteristics or only suitable for local image processing, and direction ambiguity suppression of large-area SAR images can be quickly completed while indexes such as SAR image resolution, peak sidelobe ratio and integral sidelobe ratio are not worsened and original phase information of the SAR images is reserved.

Description

technical field [0001] The invention relates to the technical field of synthetic aperture radar image quality optimization processing, in particular to a synthetic aperture radar azimuth ambiguity suppression method based on the dominant strength constraint of an antenna main lobe. Background technique [0002] Synthetic Aperture Radar (SAR) obtains high azimuth resolution through the relative motion between the sensor and the target. According to the principle of the Doppler effect, the relative motion between the radar and the target produces the Doppler frequency in the azimuth direction of the echo signal, but since SAR is equivalent to sampling with the pulse repetition frequency (PRF) as the sampling frequency in the azimuth direction, the antenna The echo with higher Doppler frequency generated by the part outside the beam width of the main lobe is under-sampled and received, forming an azimuth ambiguous signal, and then becomes a "defocused ghost target" in the two-d...

AI Technical Summary

Problems solved by technology

Severe azimuth ambiguity will affect the interpretation and interpretation of SAR images, especially in SAR marine military monitoring, the backscatter coefficient of the sea surface is relatively small, and the backscatter coefficient of coastal land, especially ships at sea, is relatively large. The azimuth blurred image of a strong scattering target will interfere with the real target on the sea surface SAR image and become a false target, which often has a serious impact on the interpretation of the SAR image

[0003] The problem of azimuth ambiguity in SAR images can generally be alleviated by optimal antenna design. However, since azimuth ambiguity is an inherent phenomenon of SAR imaging mechanism, especially for spaceborne SAR, with the continuous improvement of spatial resolution, system optimization design The difficulty of the problem has increased significantly, and the azimuth ambiguity of spaceborne SAR has gradually become one of the serious problems affecting the quality of SAR images.

At present, the methods for suppressing azimuth ambiguity from the perspective of SAR signal processing are very limited, and the three-filter suppression algorithm does not consider the influence of range migration of SAR echo signals, which cannot meet the needs of azimuth ambiguity suppression for high-resolution SAR systems (see literature [1] : Zhang Zhi-min and Wang Zhen-song, 2001, On Suppressing Azimuth Ambiguities of Synthetic Aperture Radar by Three Filters.In Proc.CIE-Int.Conf.Radar, pp.624-626); ideal filter suppression algorithm for isolated The fuzzy energy of point or centralized targets has a certain suppression effect, but it is no longer applicable to distributed or large-area scene targets (see literature [2]: Alberto Moreira, 1993. Suppressing the Azimuth Ambiguities in Synthetic Aperture Radar Images.IEEE Transaction on Geoscience and Remote Sensing, 31(4), 885-895); the suppression algorithm based on the adaptive filter depends on the accuracy of obtaining the statistical characteristics of the main signal and the fuzzy signal and requires multiple iterative operations. The processing efficiency is relatively limited (see literature [3]: Andrea Monti Guarnieri, 2005. Adaptive Removal of Azimuth Ambiguities in SAR Images. IEEE Transaction on Geoscience and Remote Sensing, 43(3), 625-633)

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