超宽带信号波形及其合成孔径雷达成像研究

【作者】 李海英；

【导师】 杨汝良；

【作者基本信息】 中国科学院研究生院（电子学研究所） ， 通信与信息系统， 2002， 博士

【摘要】 超宽带雷达因其高距离分辨率、强抗干扰能力、低截获率等优异的性能受到越来越多的关注。美国国防部近几年一直将超宽带雷达技术列为国防关键技术计划中的重要研究内容。随着现代战术武器的飞速发展和微波遥感技术的进步，超宽带合成孔径雷达（UWB SAR）现已成为国内外研究热点之一。由于雷达是综合性很强的电子系统，超宽带雷达的具体实现要受到实际硬件水平的限制，其中视频回波信号瞬时大带宽给接收机数据采集造成了很大的困难。本论文基于当前的硬件水平限制，研究在不增加接收机瞬时带宽的情况下获得超宽带回波的信号形式，探讨超宽带波形在合成孔径雷达成像中的应用。本文结合了雷达分辨理论分析了限制合成孔径雷达分辨率的因素，给出了雷达波形按模糊函数的分类与波形设计原则。本文对频率步进信号（Stepped-Frequency）及其合成孔径雷达成像进行了全面深入的研究。包括：频率步进波形合成超宽带信号分析，IFFT方法获得目标一维距离像与距离分辨率分析，径向速度对目标距离像的影响、速度补偿、频率步进信号的模糊函数分析，以及频率步进波形照射下的合成孔径雷达成像、波形设计与系统设计。主要创新在于：修正了径向速度引起的距离像展宽表达式，提出了用于合成孔径雷达成像的频率步进波形设计方法，给出了频率步进合成孔径雷达的系统设计与成像步骤。本文深入研究了脉内调频脉冲串波形（Stepped-Chirp）及其合成孔径雷达成像。分析了脉内调频脉冲串波形合成超宽带信号的可行性，给出窄带子脉冲串相参合成宽带回波、获得一维高分辨距离像的方法，分析了径向速度对目标距离像的影响，提出了速度补偿方法，推导了脉内调频脉冲串波形的模糊函数，明确了波形的分辨能力，提出了波形设计原则，分析了脉内调频脉冲串波形照射下的合成孔径雷达成像，给出了脉内调频脉冲串合成孔径雷达的系统设计思路与具体成像方法，为高分辨率合成孔径雷达系统设计与成像提供了切实可行的方案。创新点在于：提出了脉内调频脉冲串波形合成宽带回波、获得一维高分辨率距离像的方法，给出了脉内调频脉冲串合成孔径雷达成像的具体步骤。<WP=4>以上研究的两种信号形式都是通过窄带子脉冲串相参合成的方法来获得超宽带回波信号，本文还探讨了去斜率（Dechirp 或 Stretch）方法，分析了去斜率降低接收机中频带宽、FFT获得目标一维距离像的原理，并探讨了线性调频去斜率合成孔径雷达成像，给出了具体实现步骤。更多还原

【Abstract】 Ultra-Wide Band (UWB) radar is paid more attention to due to its great capabilities in high range resolution, robust anti-jamming and low probability of interception. In these years, Department of Defense of United States is always treating it as the key technique. With the development of modern weapon and the progress of microwave remote sensing technique, Ultra-Wide Band Synthetic Aperture Radar (UWB SAR) has become the hot field in the radar world.For radar is a complicated electronic system, the implementation of UWB will be subject to the level of electronic hardware. The large instantaneous bandwidth of UWB return causes great trouble to receiver. The dissertation is focused on UWB waveforms, which achieve UWB return without increasing the instantaneous bandwidth, and signal processing to generating SAR images with the desired waveform.Based on radar resolution principles, the factors working on SAR resolution are discussed. The waveforms are classified by ambiguity function, and the principle of waveform design is introduced.The stepped-frequency waveform design and stepped-frequency SAR imaging are discussed detailedly. The main work is given as follows: the stepped-frequency waveform synthesizing the wideband signal, the synthetic range profile (SRP) by IFFT, the range resolution of stepped-frequency waveform, the effect of the radial velocity on the SRP, the radial velocity compensation, ambiguity function, waveform design and stepped frequency SAR imaging and so on. The revised range spread function is validated by simulation. The method to design waveform and SAR system is described, and the steps of SAR imaging are presented.The stepped-chirp waveform and stepped-chirp SAR imaging are presented in detail. The UWB return is synthesized by a burst of narrow bandwidth chirp pulses whose carrier frequencies sequentially change. The effect of the radial velocity on synthetic spectrum and synthetic range profile is discussed, and the velocity compensation method is described. The ambiguity of stepped-chirp is presented and <WP=6>used to design the waveform. Furthermore, the stepped-chirp SAR system design and SAR imaging are discussed. Compared with chirp and stepped-frequency waveform, the advantages of stepped-chirp waveform are presented.The above waveforms discussed are to synthesize the WB or UWB with narrow band pulses. Assuming the transmitting UWB linear frequency modulation (Chirp), dechirp processing is introduced, and the method involved to obtain high resolution by reducing the IF bandwidth is presented. Furthermore, dechirp processing used to SAR imaging is discussed, and the processing steps are described.更多还原