A Method for Precise Estimation of Doppler Modulation Frequency in High Squint Sar Imaging Mode

Abstract

The invention relates to a method for accurately estimating the Doppler rate in a large-strabismus SAR imaging mode. The method comprises the steps that 100) distance walk compensation, distance bending correction and secondary distance compression are implemented on echo data to obtain a double-time-domain signal which is compressed in the distance direction; 101) a dechirp processing is implemented on the distance compressed data in an orientation time domain by utilizing a reference function Sdechirp(t); 102) FFT (Fast Fourier Transform) is implemented on the orientation direction data to change the data from the orientation time domain to an orientation frequency domain; 103) a special display point is selected from each distance door in a maximal energy method, the orientation-direction position of the point is estimated, and a compensation function Scomp(t) of each special display point is calculated according to the orientation-direction position; 104) windowing is implemented, data within the main fuzzy width of the special display point selected from each distance door is reserved, and data which has no contribution to estimation of the Doppler rate is abandoned; 105) reverse Fourier transformer is implemented, and space change phase is compensated in the orientation time domain; and 106) the Doppler rate is estimated in a classic MD algorithm.

Description

technical field [0001] The invention belongs to the technical field of radar, in particular to a method for accurately estimating Doppler modulation frequency in a high squint SAR imaging mode. Background technique [0002] Synthetic aperture radar (SAR) synthesizes a large aperture by coherently accumulating echo data to obtain high-resolution images. It has the characteristics of all-weather (except heavy rain), all-day, independent range resolution and long-distance, wide swath imaging, which can significantly improve the information acquisition ability of radar. Synthetic aperture radar can generally be divided into front and side-looking mode and squint mode according to different beam center points. In the SAR imaging mode with a large oblique viewing angle, the center of the antenna beam points to the imaging scene area at a large angle with the side-looking direction. Therefore, the large oblique viewing angle mode has a high potential for ground target detection an...

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Problems solved by technology

[0003] The purpose of the present invention is to apply the idea of ​​MD algorithm, propose a method for accurately estimating the Doppler modulation frequency in SAR imaging mode after compensating the space-varying phase and then estimating the Doppler modulation frequency, so as to solve the problem of In the SAR imaging mode with a large oblique angle of view, the Doppler modulation rate cannot be accurately estimated due to the space-varying phase error in the azimuth, so that the Doppler modulation rate of the distinctive point after compensation for the space-varying phase can be accurately estimated

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