Near space circular synthetic aperture radar rapid back-direction projection imaging method

Abstract

The invention discloses a near space circular synthetic aperture radar rapid back-direction projection imaging method. In view of the problem of near space circular synthetic aperture radar rapid imaging, the method replaces a phase error in coherent imaging method with a pixel amplitude error as the evaluation criterion of imaging precision, approximately expands through low order of Green function which is based on chebyshev nodes and lagrange interpolation according to the principle of minimum mean square error, switches the problem of calculation of sub aperture projection to the problem of calculation of limited number of approximate expansion coefficients, and reduces as much as possible the number of expansion coefficients under the condition of meeting the focusing accuracy so that algorithm computational complexity is reduced, and then accomplishes the imaging from coarse focusing to fine focusing by applying recursive computation. Compared with the existing circular SAR back-direction projection imaging method, the near space circular synthetic aperture radar rapid back-direction projection imaging method has the advantages that computing speed is greatly improved, big scene imaging is achieved and imaging accuracy is much higher.

Description

technical field [0001] The invention belongs to the technical field of radar and relates to a synthetic aperture radar imaging method technology, in particular to a fast back projection imaging method in the near space circumference synthetic aperture radar imaging technology. Background technique [0002] Synthetic Aperture Radar (SAR) is an all-weather, all-weather modern high-resolution microwave remote sensing imaging radar. In fields such as change detection, SAR has played an increasingly important role. [0003] Near-space circular synthetic aperture radar (CSAR) has many outstanding advantages because it can perform long-term observations around the imaging area. It can realize rapid observations of large-area areas in a relatively short period of time, and has high observation efficiency. In addition, since the adjacent space CSAR performs 360° observation of the observation area, the imaging resolution can be effectively improved. [0004] In the circular traject...

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Problems solved by technology

[0004] In the circular trajectory mode, due to the special form of the platform flight trajectory, the azimuth spectrum of the radar echo is difficult to derive, so it is applied to the frequency domain imaging algorithm of the general linear SAR mode, such as range Doppler, Chirp Scaling and wave number domain, etc. None of the algorithms can be directly applied to CSAR

The frequency domain algorithm that can be used for near-space CSAR imaging is an improved wavenumber domain algorithm. In the literature: A Novel Modified Omega-K Algorithm for Circular trajectory Scanning SAR Imaging Using Series Reversion, Yi Liao, Meng-dao Xing, Lei Zhang, Zheng Bao, "EURASIP Journal on Advances in Signal Processing", 2013: 64, proposed a wavenumber domain method based on sequence inversion, the imaging effect is more accurate, but the process of calculating the two-dimensional wavenumber domain spectrum of this method is more complicated, and The complexity of the algorithm is N2.5 (where N is the size of the square data matrix), which cannot achieve fast imaging; another imaging method is the back-projection algorithm, and the traditional back-projection method takes a long time to calculate. In the literature: Processing of Circular SAR Trajectories with Fast Factorized Back-Projection, Octavio Ponce, Pau Prats, Marc Rodriguez-Cassola, Rolf Scheiber, Andreas Reigber, "Geoscience and Remote Sensing Symposium (IGARSS) 2011IEEE International", 2011: 3692-3695, using fast block Back projection method, the algorithm complexity is reduced to N 2 log(N), and achieve the focusing effect by limiting the projection phase error, effectively improving the back-projection algorithm, and this algorithm only considers the projection phase error, ignoring the pixel amplitude error of the point

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