Parameterized self-focusing method for compensating impact on GEOSAR imaging from background ionized layer

Abstract

The invention discloses a parameterized self-focusing method for compensating the impact on GEOSAR imaging from a background ionized layer, and the method comprises the steps: firstly carrying out the range pulse compression of raw echo data of GEOSAR through matched filtering; selecting a rectangular region in a GEOSAR imaging region, and carrying out grid division; secondly carrying out envelope alignment and phase compensation of the GEOSAR data after range pulse compression, and calculating the coefficient of the background ionized layer relative to a high-order change function along with orientation slow time through a law of image minimum entropy; finally judging whether the iteration is ended or not; carrying out the enveloping and phase compensation of all imaging regions through the high-order change function obtained through iteration if the iteration is ended, thereby achieving the GEOSAR imaging in the region. The method achieves echo envelop walk correction and phase error compensation, which are caused by the high-order change of the background ionized layer, in a mode of iteration through employing the characteristic that the variation tendency of the background ionized layer in a GEOSAR synthetic aperture time can be approximated to be a polynomial based on the law of image minimum entropy, thereby effectively improving the GEOSAR imaging quality.

Description

technical field [0001] The invention relates to a method for compensating the influence of the background ionosphere on GEOSAR imaging, in particular to a parametric self-focusing method for compensating the influence of the background ionosphere on GEOSAR imaging, belonging to the field of geosynchronous orbit SAR system development. Background technique [0002] Geosynchronous orbit SAR has outstanding advantages such as wide coverage and fast revisiting speed, and has great application prospects in many fields such as earthquake disaster reduction and environmental monitoring. However, due to the high orbit and slow speed of the satellite, its synthetic aperture time reaches the order of hundreds of seconds or even thousands of seconds (in contrast, the synthetic aperture time of low-orbit SAR is on the order of seconds). Inside, there are many non-ideal factors that will lead to decoherence between target echoes, thereby reducing the imaging quality of GEOSAR, and the te...

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Problems solved by technology

However, for GEOSAR, the number of transmitted and received pulses in the synthetic aperture time is as high as tens of thousands or even hundreds of thousands. It is almost impossible to search for relative changes in the ionosphere in such a large space, so it cannot be directly applied to GEOSAR imaging processing.

[0005] In short, the compensation for the ionosphere is one of the most critical technologies for the realization of GEOSAR. So far, no effective compensation method has been proposed at home and abroad, so this problem is still a hot and difficult problem in GEOSAR research.

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