基于合成孔径三维成像的雷达散射截面测量技术研究

发布时间：2018-01-10 01:04

本文关键词：基于合成孔径三维成像的雷达散射截面测量技术研究　出处：《电子科技大学》2016年博士论文　论文类型：学位论文

【摘要】：为了满足日益增长的目标遥感、识别、侦察与反侦察的应用需求,目标雷达散射截面(RCS)测量方法的研究逐渐成为热点之一。由于电磁计算手段对于复杂及复合材料目标的RCS计算非常困难,实际测量是最有效和最准确的手段。但是,传统的远场实测和紧缩场实测存在成本高、环境影响大或者目标大小受限等问题。三维合成孔径雷达(SAR)成像作为一种新型的目标散射系数分布测量技术,在解决以上问题时有巨大的优势。本文以三维SAR成像技术为基础,以基于合成孔径三维成像的RCS测量技术为主要研究内容,针对近远场变换、回波相参性缺失和运算量大等问题,研究并提出了基于综合平面波三维成像的RCS近场测量方法、基于稳态表面电磁流模型三维成像的RCS测量方法及基于子孔径逼近的快速算法。本文主要工作和创新总结如下:1、研究了基于合成孔径三维成像的RCS测量基本原理,提出了目前面临的主要问题,分析了该技术的优势。首先从三维线阵SAR成像原理入手,介绍了其几何结构及信号模型,为RCS测量新方法提供了理论基础,并分析了成像算法,指出了三维后向投影(BP)算法精度高但运算量大的问题。其次,联合分析了目标电磁散射的区域划分、RCS的定义及线阵SAR的三维分辨率,指出了基于高分辨SAR成像的RCS测量必然在近场进行、须进行近远场变换的问题,并以散射中心模型为切入点,提出了大合成孔径角下回波相参性缺失的问题。最后,通过与基于一维、二维成像的RCS测量技术的对比分析,说明了基于三维成像的RCS测量具有三维分辨能力的优点,可以提取目标感兴趣部分的RCS,或者分离环境噪声,适用于外场测量,测量成本低,并利用实测实验验证了这一优点。2、针对在近场测量的需求,提出了基于综合平面波三维成像的RCS测量方法,能够反演目标的远场RCS。首先,利用基于综合平面波的近远场变换数字信号处理技术,在线阵SAR近场测量的系统架构下实现了入射波与散射波的近远场变换,满足了远场RCS的测量要求。其次,改进了BP算子,提出了基于改进BP算子的综合平面波近远场变换方法,并推导了基于改进BP算子的综合平面波三维SAR成像模型,使得其能够同时实现近远场变换和三维成像。再次,建立了基于综合平面波三维成像的RCS测量方法,可以从微波三维图像中,提取目标特征,并反演目标远场RCS在不同角度、不同频率的值,仿真验证了该方法的部分RCS提取能力和测量精度。最后,针对传统基于综合平面波的近远场变换技术在稀疏阵列下不适用的缺点,验证了基于改进BP算子的综合平面波近远场变换方法在稀疏阵列下仍然有效,并且能够准确反演出目标远场RCS。3、针对回波相参性缺失问题,提出了基于稳态表面电磁流模型三维成像的RCS测量方法,能够提高大合成孔径角下的RCS测量精度。首先,通过对实测数据的分析发现,腔体、角反射器等类型目标在大合成孔径角下的回波会产生相位逆转现象,并导致散射中心模型失效进而影响RCS测量精度。其次,针对该问题,提出了固定发射源的解决方案,并基于此建立了基于稳态表面电磁流的成像模型,通过推导证明了微波三维图像是对目标表面电流密度与磁流密度的联合估计。最后,将稳态表面电磁流成像模型应用于RCS测量,提出了基于稳态表面电磁流模型三维成像的RCS测量方法。与基于综合平面波三维成像的RCS测量方法相比,该方法可以消除回波相位逆转现象,提高大合成孔径角下的RCS测量精度,但是分辨率和测量效率较低。因此,两种方法可以相互补充,集成在一套测量系统中,适应不同的测量要求。4、针对运算量大的问题,提出了基于子孔径逼近的快速算法,能够提高数据处理效率。首先,从三维BP算法的原理出发,结合微波三维图像的稀疏特性,指出了三维BP算法的逐点扫描会带了很多无用的运算量。其次,提出了利用子孔径、低分辨成像,提取目标散射点所在区域的先验信息,以剔除无用运算量,提升高分辨成像效率的子孔径逼近快速算法,并利用实测数据验证了该算法的有效性。然后,对运算量进行分析,指出一但确定了最优的子孔径选择方式,该算法的运算量只与目标的特性(目标结构和场景稀疏度)相关。针对大场景成像,一般稀疏度非常大,当稀疏度大于97.6%时,子孔径逼近快速算法运算量只相当于BP算法运算量的十分之一左右。最后,将子孔径逼近快速算法应用于RCS测量,得到了可靠的结果,提升了RCS测量的数据处理效率。总之,本文建立了基于合成孔径三维成像的RCS测量基本原理,并在近远场变换、测量模型和算法效率优化等方面取得了一系列有价值的研究成果,为新型RCS测量技术的研究和应用提供了重要的理论指导和技术支持。
[Abstract]:In order to meet the target of remote sensing, the growing demand for recognition, application of reconnaissance and anti reconnaissance, radar cross section (RCS) measurement methodology research has become a hot topic. Because of the electromagnetic calculation method for complex and composite target RCS is very difficult to calculate, the actual measurement is the most effective and accurate means. However, the traditional far field measurement and tight field measurement of high cost, environmental impact or target size limitation. Three dimensional synthetic aperture radar (SAR) imaging as a new target scattering coefficient distribution measurement technology in solving the above problem have great advantages. Based on the 3D SAR imaging technique based on RCS the measurement technology of synthetic aperture imaging based on the main research content, aiming at the problem of near to far field transformation, the lack of coherent echo and the large amount of computation, based on the comprehensive study and put forward the plane Wave 3D imaging RCS near field measurement method based on RCS measurement method of electromagnetic steady-state surface flow model of 3D imaging and fast algorithm based on sub aperture approximation. The main work and innovation are summarized as follows: 1, research on the basic principle of RCS synthetic aperture imaging based on 3D measurement, put forward the main problems currently facing, analysis the advantage of this technology. Starting from the 3D linear array SAR imaging principle, introduces the geometric structure and signal model, and provides the theoretical basis for the new RCS measurement method, and analyzed the imaging algorithm, points out the three-dimensional backward projection (BP) algorithm with high precision but large computing problems. Secondly, the joint analysis the division of the target electromagnetic scattering, 3D resolution definition and linear SAR RCS, pointed out that the RCS measurement of high resolution SAR imaging based on the inevitable in the near field, be near to far field transformation problem, and scattering The center of the model as a starting point, put forward the synthetic aperture angle echo coherence of the missing issues. Finally, through comparative analysis of RCS measurement based on 1D, 2D imaging technology, the measurement of 3D imaging based on RCS has the advantages of three-dimensional resolution, you can extract the target of interest part of RCS, or separation environmental noise, suitable for field measurement, low measurement cost, and verifies the advantages of.2 by experiment, for in the near field measurement. The proposed RCS measurement method of 3D imaging based on synthetic plane wave, to the far field RCS. inversion target first, using the near far field transformation of digital signal processing technology the plane wave based on the linear SAR near field measurement system under the framework of the near and far field transformation of incident wave and scattered wave, the far field RCS meet the measurement requirements. Secondly, the improved BP operator, is proposed based on Synthetic plane wave improved BP operator near far field transformation method, and presents an improved BP operator synthetic plane wave model based on 3D SAR imaging, which can realize both the near and far field transform and 3D imaging. Thirdly, the establishment of a comprehensive three-dimensional plane wave imaging method based on RCS, from microwave in 3D images and the target feature extraction, and the inversion of the target far field RCS at different angles, different frequency values, the simulation results show that RCS part of the extraction ability and measurement accuracy. Finally, aiming at the near to far field transformation technology based on synthetic plane wave in sparse array under the disadvantage, verified the synthesis of planar improved BP operator the wave near to far field transformation method based on sparse array is effective, and can accurately inverse the target far field RCS.3, aiming at the problem of the lack of coherent echo, the steady-state surface electric magnetic flow model based on three RCS dimensional imaging measurement method, which can improve the measurement accuracy of RCS large aperture angle. Firstly, by the analysis of the data found that the cavity corner reflector type in a large synthetic aperture angle of the echo will cause the phase reversal phenomenon, and lead to the failure of scattering center model can affect RCS measurement accuracy. Secondly in order to solve the problem, and proposed solutions to fixed emission sources, and based on the established model of electromagnetic imaging based on the steady flow surface, it proves that the three-dimensional image is combined with microwave flow density estimation on target surface current density and magnetic. Finally, the application of electromagnetic steady-state surface flow imaging model in RCS measurement. The RCS measurement method of electromagnetic steady-state surface flow model of 3D imaging based on RCS. Compared with the measurement method of synthetic plane wave based on 3D imaging, the method can eliminate echo phase reversal phenomenon, To improve the measurement accuracy of RCS large aperture angle, but the resolution and the measurement efficiency is low. Therefore, the two methods can complement each other, in an integrated measurement system, meet the measurement requirements of different.4, aiming at the problem of large amount of computing, we propose a fast algorithm based on sub aperture approximation, can improve the data processing efficiency. First, starting from the principle of 3D BP algorithm, combined with the characteristics of microwave sparse 3D images, pointed out that the 3D BP algorithm scanning point will bring a lot of useless computation. Secondly, proposed the use of sub aperture, low resolution imaging, extraction of target scattering point prior information, to eliminate useless operation the amount, enhance the sub aperture high resolution imaging efficiency and fast approximation algorithm, using the measured data to verify the validity of the algorithm. Then, the calculation analysis, pointed out that a sub aperture but to determine the best choice The characteristics, the computational time only with the target (target structure and sparsity. Aiming at the scene) large scene imaging, general sparse degree is very large, when the sparsity is greater than 97.6%, the sub aperture approximation algorithm is only equivalent to the fast BP algorithm is about 1/10. Finally, the sub aperture approximation fast algorithm is applied in RCS measurement, obtained the reliable results, enhance the RCS measurement data processing efficiency. In conclusion, this paper establishes the basic principle of RCS synthetic aperture imaging based on 3D measurement, and in the near and far field transformation, the measurement model and algorithm efficiency optimization has obtained a series of valuable research results, provide the theoretical guidance and technical support for the research and application of the new RCS measurement technology.

【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN957.52

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