Curvilinear track SAR squint imaging method based on improved slant distance model

Abstract

The invention belongs to the technical field of radar imaging, and discloses a curvilinear track SAR squint imaging method based on an improved slant distance model. The curvilinear track SAR squint imaging method based on the improved slant distance model comprises the specific steps that an equivalent slant distance model is established; a two-dimensional spectrum is derived; the distance walking momentum is calculated and is transformed to the distance frequency domain to complete the distance walking correction in the distance direction; an echo signal in the distance frequency domain is subjected to the fourier transformation in the azimuth direction, and a two-dimensional spectrum of the echo signal is obtained; distance compression, secondary distance compression and distance bending correction are carried out, and the echo signal is subjected to inverse fourier transformation in the distance direction; and an azimuth frequency domain signal is subjected to azimuth compression and inverse fourier transformation in the azimuth direction, and imaging results are obtained. According to the curvilinear track SAR squint imaging method based on the improved slant distance model, on the basis of motion characteristics of a curvilinear track platform, the equation of motion of the curvilinear track platform is subjected to high-order approximation, a four-order equivalent slantdistance model expression is established, based on the slant distance model, the analytical solution of the two-dimensional spectrum of the curvilinear track platform is derived, the conciseness and the high precision of a frequency spectrum is ensured, and full-aperture high-resolution imaging can be achieved.

Description

technical field [0001] The invention belongs to the technical field of radar imaging, and in particular relates to a curved trajectory SAR strabismus imaging method based on an improved slant range model. Background technique [0002] At present, the existing technologies commonly used in the industry are as follows: Synthetic Aperture Radar (SAR) is a microwave imaging radar with high resolution capability, which can work all day, all weather, and long distances, and has been widely used in various mobile platforms. Such as airborne SAR, missile-borne SAR. For high-speed moving platforms such as missiles, due to the large velocity and acceleration of the missile body, the motion trajectory no longer meets the straight line approximation, and the expression of the slant range of the missile-borne SAR is more complicated, making it difficult to directly use the stationary phase point method (POSP) to solve the signal. Two-dimensional spectrum, at this time, it is difficult f...

AI Technical Summary

Problems solved by technology

For high-speed moving platforms such as missiles, due to the large velocity and acceleration of the missile body, the motion trajectory no longer satisfies the linear approximation, and the expression of the slope distance of the missile-borne SAR is relatively complicated, making it difficult to directly use the stationary phase point method (POSP) to solve the signal Two-dimensional spectrum, at this time, the conventional SAR imaging algorithm has been difficult to achieve precise focus on the target

Literature 1 proposes a SAR imaging method based on the range-Doppler algorithm under the condition of the diving trajectory, which can realize the imaging processing of non-linear apertures, but its ability to deal with large squints is poor, and the imaging accuracy is low

Document 2 proposes a method of deriving the two-dimensional spectrum by using series inversion. Under the condition that the slant range is expanded into a slow time fourth-order approximation, the series inversion method is used to obtain the height of the stationary phase point in the form of series expansion. The first-order approximate solution improves the imaging accuracy of missile-borne SAR, but its two-dimensional spectrum is in the form of series expansion, which is not concise enough and is not convenient for the design of subsequent imaging algorithms

Document 3 proposes an algorithm based on sub-aperture imaging processing, but sub-aperture processing cannot obtain high resolution

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