A sub-aperture isar imaging method for high-orbit ship targets

Abstract

The invention discloses a high-orbit ship target sub-aperture ISAR imaging method, which solves the problem that the synthetic aperture time required for high-orbit satellites to achieve high-resolution imaging reaches hundreds of thousands of seconds due to the high orbital height and relatively low operating speed. In the long synthetic aperture time, the ship motion causes the image to defocus, and the resolution is difficult to effectively improve the problem. In order to solve this problem, on the one hand, the sub-aperture synthetic aperture time is short, which reduces the impact of ship motion on imaging. , On the other hand, the rotation angle generated by the ship's sway also helps to achieve high-resolution ISAR imaging. The invention breaks through the traditional understanding of ship motion as motion error, and uses ship motion for high-resolution ISAR imaging, which solves the contradiction between high-orbit long synthetic aperture time and ship motion, and can be used for high-speed In the field of orbital ship target detection, recognition and imaging.

Description

technical field [0001] The invention relates to a sub-aperture ISAR imaging method for a high-orbit ship target, which belongs to the field of radar technology, and further relates to a synthetic aperture radar imaging signal processing technology, which can be used in the fields of high-orbit ship target detection, identification and imaging. Background technique [0002] High-orbit satellites obtain observation advantages such as large-scale coverage and fast revisiting in ultra-high orbits, and have great application potential in the field of remote sensing mapping. [0003] While ultra-high orbit brings observation advantages to high-orbit satellites, it also brings many problems to imaging processing. Ultra-high orbits first lead to high-orbit satellites needing hundreds of thousands of seconds of synthetic aperture time to achieve azimuth high-resolution imaging, and the satellite orbit is curved during long synthetic aperture time, which cannot be approximated as a st...

AI Technical Summary

Problems solved by technology

Ultra-high orbits first lead to high-orbit satellites needing hundreds of thousands of seconds of synthetic aperture time to achieve azimuth high-resolution imaging, and the satellite orbit is curved during long synthetic aperture time, which cannot be approximated as a straight line. The distance model is no longer a simple quadratic curve model; secondly, the ultra-high orbit leads to a long distance between the satellite and the earth, and a long propagation delay of the echo signal. The "stop-go" assumption is no longer valid, so the traditional frequency domain imaging Algorithms are no longer capable of effective imaging processing

Under the condition of considering the earth's rotation and propagation delay, by improving the traditional frequency-domain algorithm or using the time-domain BP algorithm, the static scene target imaging can be realized, while the ship target is moving on the sea surface, and the ship target can be imaged within a long synthetic aperture time. In addition to the translational motion of its own navigation, the ship target will also perform multi-period three-dimensional rocking motions. Affected by the real-time wind and waves on the sea surface, the three-dimensional rocking motion characteristics of the ship target are unknown, and the nonlinear three-dimensional Rocking motion is difficult to compensate, resulting in the inability to achieve coherent accumulation of echo signals, which affects the effective improvement of imaging resolution

[0004] At present, there is no public research on high-orbit long synthetic aperture time ship target imaging at home and abroad. Therefore, there is an urgent need for an imaging method that can solve the contradiction between high-orbit long synthetic aperture time and ship motion. One of the important issues to be considered in applications such as target detection and surveillance

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