【作者】 师君；

【导师】 张晓玲； 杨建宇；

【作者基本信息】 电子科技大学 ， 信号与信息处理， 2009， 博士

【摘要】 由于具有全天候、全天时等优点，合成孔径雷达(SAR)在地球观测、环境监测及军事侦察等方面具有重要意义。为提高SAR系统性能，扩展其应用水平，国际上开展了新型SAR技术研究。双基地合成孔径雷达是指发射系统和接收系统位于不同平台上的新型合成孔径雷达。与单基地SAR相比，双基地SAR具有可获得目标区域非后向散射特征、系统设计灵活及便于接收机隐身设计等优点。线阵SAR是指通过平台运动与阵列天线合成虚拟二维面阵天线，并结合脉冲压缩技术获得观测场景散射系数三维分布的新型合成孔径雷达。线阵SAR可实现对观测区域的三维成像；并能有效解决传统SAR存在的阴影效应，实现对陡变地形的观测。因此，作为两种新型合成孔径雷达，双基地SAR和线阵SAR具有广泛的军事和民用前景。本文在国家自然基金和国家863项目支撑下，开展了双基地SAR和线阵SAR原理与成像处理技术研究。在原理研究方面，本文从回波信号空域特征入手，采用矢量分析技术，利用“等距离历史集”、“投影(椭)圆”、“投影线”、“模糊函数”、“模糊域”等概念建立了单基地SAR和双基地SAR从三维观测空间到二维图像空间的映射关系，解释了合成孔径雷达成像的本质，讨论了不同模式下双基地SAR分辨率的空变特征。通过对模糊函数的分析，研究了全阵元线阵SAR原理。针对全阵元线阵SAR系统复杂、成本高的缺点，提出了单激励线阵SAR系统。从回波信号空域特征入手，解释了单激励线阵SAR具有三维成像能力的原因，并对其模糊函数进行了分析，发现了影响单激励线阵SAR模糊函数的主要因素：线阵长度和天线相位中心切换模式。研究了周期函数和伪随机切换模式对单激励线阵SAR模糊函数的影响，并采用拉格朗日乘数法，对单激励线阵SAR天线相位中心切换模式进行了优化设计，获得了最小均方误差准则下的最优设计。在成像处理方面，本文研究了双基地SAR时域成像处理技术，实现了对双基地SAR实测数据成像处理，获得了双基地SAR图像。分析了运动误差对移变双基地SAR成像的影响，为移变双基地SAR运动参数估计方法研究提供了重要的理论指导。针对双基地SAR分辨率的空变特征，提出了基于变尺度逆傅里叶变换的双基地SAR距离—多普勒算法，为移变双基地SAR快速算法设计提供了新的思路。研究了线阵SAR及单激励线阵SAR时域成像处理技术，实现了单激励线阵SAR实测数据成像处理，获得了观测场景的三维图像，验证了单激励线阵SAR原理的正确性。针对线阵SAR图像为三维空间中某特定连续曲面的特点，提出了基于曲面预测的线阵SAR快速成像算法，大大提高了线阵SAR成像处理效率。最后，基于离散信号的矩阵模型，提出了基于正交子空间投影的基—N多分辨逼近方法，并将该方法应用于线阵SAR分辨率融合，提出了基于正交补子空间分解的线阵SAR基—N分辨率融合方法，为解决线阵SAR切航迹向分辨率较低的问题提供了新的途径。总之，本文建立了双基地SAR及线阵SAR的原理，提出了双基地SAR及线阵SAR快速成像处理方法和线阵SAR分辨率融合方法，为双基地SAR及线阵SAR系统研究提供了重要的理论指导和技术支持。更多还原

【Abstract】 With the ability of all-day and all-climate observation, synthetic aperture radar (SAR) plays an important role in earth observation, environment monitor and reconnaissance fields. To improve its capability and application fields, research on the novel SAR systems has been carried out in the radar field. Bistatic SAR is a kind of synthetic aperture radar whose transmitter and receiver are mounted on difference platforms. Compared with monostatic SAR, bistatic SAR can obtain the target’s non-backscattering feature, make the design of the transmitter and receiver more flexible and is beneficial for the receiver platform’s stealth design. LASAR is a kind of synthetic aperture radar that synthesizes a 2-D virtual array by mounting a linear antenna array on a moving platform to obtain the 3-D RCS distribution of the observation scene by combining with the pulse compression technique. Compared with traditional SAR, LASAR can obtain the observation scene’s 3-D image, and overcome the shadow-effect of traditional SAR, which is good at observing the steep area. Thus, bistatic SAR and LASAR could widely be used in both military and civilian fields.Sponsored by the National Natural Science Foundation of China and the 863 national projects, this dissertation researches the principles and imaging techniques of the bistatic SAR and LASAR.In the aspect of principle, this dissertation builds the mapping between the 3-D observation scene and 2-D image space using the concept "equiv-range-history set", "circle-projection", "ellipse-projection ", "perspective line", "ambiguity function" and "ambiguity region", reveals the essence of synthetic aperture radar, and discusses the space-variant feature of bistatic SAR. Then, the ambiguity function of full-element LASAR is analyzed to explain the reason that it can produce 3-D resolution. To overcome the disadvantages of full-element LASAR, such as, high cost and complex system architecture, the concept of "one-active" LASAR is proposed. By analyzing the spatial feature of "one-active" LASAR echo, the reason that "one-active" LASAR can produce 3-D resolution is explained; then based on the discussion on the ambiguity function of "one-active" LASAR, the main factors affecting its system performance have been found, i.e., length of the linear array and the switch mode of the antenna phase centre. Then the switch mode is optimized by the Lagrange multiplier method under the minimum variance criterion, and we find that when the switch mode obeys the parabolic distribution, the cross-range 2-D AF is optimal.In the aspect of imaging technique, the time-domain imaging method of bistatic SAR is researched and employed in bistatic SAR experiment data processing, and the imaging results of bistiatic SAR are obtained. Then the motion measure errors of bistatic SAR are discussed, and the main errors cause bistatic SAR defocus have been found, which is important for the design of bistatic SAR motion error estimation method. To eliminate the space-variant feature of bistatic SAR. the scaled IFFT Range-Doppler method is presented in the dissertation, which provides a new idea for the design of transitional-variant bistatic SAR imaging method. The time-domain imaging method of LASAR is researched and employed in "one-active" LASAR experiment data processing; and the 3-D RCS distribution of observation scene has been obtained, which demonstrates the feasibility of "one-active" LASAR. Based on the assumption that the illuminated scatterers combine a surface in the imaging space, the surface-tracing-based LASAR 3-D imaging technique has been proposed, which can reduce the computational cost greatly. Finally, based on the matrix expression of discrete signal, a radix-N multi-resolution approximation method has been proposed, and is used in "one-active" LASAR resolution fusion. The radix-N resolution fusion method proposed in this dissertation provides a new way to improve cross-track resolution of LASAR.In a word, this dissertation builds the principles of bistatic SAR and LASAR, proposes their imaging methods and resolution fusion method for LASAR. The research results are useful for the design of bistatic SAR and LASAR system and imaging algorithms.更多还原