An Imaging Method of Nonlinear Frequency Modulation Scaling for Synthetic Aperture Radar

Abstract

The invention belongs to an imaging method for nonlinear frequency modulation label change in the synthetic aperture radar imaging technology, which comprises the steps of two-dimensional frequency domain unfolding, filtering processing, nonlinear frequency modulation label change, distance compression, distance migration correction, rest phase compensation and position compression. In the method of the invention, the characteristics of orthogonality and minimum square error of the Legendre polynomials are utilized for carrying out three-order unfolding on the two-dimensional frequency domain signals of the obtained echo signals according to the Legendre orthogonality polynomials, and then, the focusing imaging on targets is realized through carrying out filtering processing and the like on three-order phase items in echo signal two-dimensional frequency domain expression. When the method of the invention is adopted, the maximum phase error under the same condition is less than 0.2 percent of the maximum phase error in the prior art, so the assurance is provided for the high-precision imaging under the large-inclination view angle condition. Therefore, the method of the invention has the characteristics that the phase error in the imaging process can be effectively reduced, the imaging processing of the large-inclination view angle is realized, in addition, the imaging effect is good, the imaging processing efficiency and the precision are high, and the like.

Description

technical field [0001] The invention belongs to the field of synthetic aperture radar (Synthetic Aperture Radar, SAR) imaging technology, in particular to the use of Legendre (Legendre) orthogonal polynomials to the nonlinear chirp scaling (Nonlinear Chirp Scaling, NCS) method of synthetic aperture radar An imaging processing method for three-order expansion of two-dimensional frequency domain signals. Background technique [0002] Synthetic aperture radar is a high-resolution imaging radar. Its principle is to form an equivalent antenna aperture through the movement of the platform, so as to obtain high azimuth resolution; resolution. Compared with optical sensors, SAR has all-day and all-weather working capabilities, and has been widely used in the fields of earth remote sensing, ocean research, resource exploration, disaster forecasting, and military reconnaissance. [0003] The basic principle of SAR imaging is to complete the pulse compression of the range signal thro...

AI Technical Summary

Problems solved by technology

In the processing process of NCS imaging method, the third-order expansion of Taylor polynomial is performed on the two-dimensional frequency domain signal of the echo signal. Approximate processing is used in the expansion process, the phase error is large, and the imaging accuracy is not high; If you want to improve the imaging processing accuracy and image the target at a large oblique angle of view, you must expand the two-dimensional frequency domain signal of the echo signal to the fourth order or higher than the fourth order Taylor polynomial, although the imaging accuracy can be achieved at this time Requirements, but there are defects such as complex imaging processing methods, low imaging efficiency and accuracy

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