脉冲合成宽带雷达目标检测算法设计与实现

发布时间：2018-10-29 11:11

【摘要】：步进频率(Stepped-Frequency,SF)雷达是一种通过多脉冲合成实现距离高分辨的宽带雷达体制,它通过发射一组载频线性跳变的雷达脉冲,再对脉冲回波进行傅里叶逆变换(Inverse Fast Fourier Transform,IFFT)处理,获得大的合成带宽,从而实现距离高分辨的效果[1]。步进频率信号的发射、接收和处理均可用窄带实现,降低了对雷达各部分瞬时带宽的要求。在保证雷达系统达到高性能指标的同时,减小了数字信号处理机硬件部分的设计难度,易于工程实现,因此得到广泛的应用。本文首先给出了步进频率信号的数学模型,对其进行推导、分析,得出步进频率信号距离高分辨的原理。针对步进频率信号参数设置产生像冗余和像缺损的问题,提出了像拼接算法。像拼接算法可以减小目标距离走动并抑制虚假目标的产生,通过与常规像拼接算法的对比和对现有技术的改进,提出了一种改进的距离域高分辨成像算法,将此应用于仿真数据与实测数据,得到真实且完备的一维高分辨距离像,完成步进频率体制雷达一维高分辨距离像成像算法的研究工作。目标的一维高分辨距离像描述了目标强散射中心在径向上的投影,它能够反映出不同物体在几何形状和层次结构上的特征和差异,可以利用一维高分辨距离像,即距离扩展目标所具有的形状和结构特征进行目标检测。距离扩展目标不同于传统的“点目标”,需采用距离扩展目标的恒虚警(Constant False Alarm Rate,CFAR)检测算法进行检测。本文在介绍了低分辨雷达恒虚警检测的基本算法、分析了算法性能的基础上,提出了三种距离扩展目标的恒虚警检测算法,通过检测性能曲线和对实测数据处理结果的对比,验证了基于顺序统计量的多通道检测算法在对数正态杂波背景下的检测性能最佳。通过对多种恒虚警检测算法的分析,选取在低分辨雷达下性能最优的单元平均恒虚警检测算法和在高分辨雷达下性能最优的基于顺序统计量的多通道检测算法应用于FPGA(Field-Programmable Gate Array)工程实现。FPGA作为新兴的信号处理元件,集成度高、速度快,具有高可靠性和稳定性,能够完成复杂的时序设计。利用FPGA并行处理等优势,分析两种应用于不同对象的恒虚警检测算法的特点,合理分配资源,综合考虑数据量与运行速度等因素,完成算法的工程设计。本文最后对提出的像拼接算法和恒虚警检测算法进行总结,完成了步进频率信号从成像到检测的数据处理过程。
[Abstract]:Step Frequency (Stepped-Frequency,SF) radar is a kind of wideband radar system with high range resolution realized by multi-pulse synthesis. It transmits a group of carrier frequency linear jump radar pulses, and then carries out Fourier inverse transform (Inverse Fast Fourier Transform,) to the pulse echo. IFFT) to obtain a large synthetic bandwidth, thus achieving the effect of high range resolution [1]. The transmit, receive and process of step frequency signal can be realized by narrow band, which reduces the requirement of instantaneous bandwidth of radar. At the same time, the design difficulty of the hardware part of the digital signal processor is reduced, and it is easy to be realized in engineering, so it is widely used. In this paper, the mathematical model of step frequency signal is given, and the principle of high resolution of step frequency signal is obtained by deducing and analyzing it. To solve the problem of image redundancy and image defect caused by step frequency signal parameter setting, an image mosaic algorithm is proposed. The image mosaic algorithm can reduce the moving distance of the target and suppress the false target. By comparing with the conventional image mosaic algorithm and improving the existing technology, an improved high-resolution imaging algorithm in range domain is proposed. The real and complete one-dimensional high-resolution range profile is obtained by applying this method to the simulation data and the measured data, and the research work of the one-dimensional high-resolution range profile imaging algorithm for stepped frequency radar is completed. The one-dimensional high-resolution range profile of the target describes the radial projection of the strong scattering center of the target. It can reflect the characteristics and differences of different objects in geometric shape and hierarchical structure, and can be used to use the one-dimensional high-resolution range profile. The shape and structure features of the extended target are used to detect the target. The extended range target is different from the traditional "point target". It is necessary to use the CFAR (Constant False Alarm Rate,CFAR (constant false alarm rate) detection algorithm to detect the extended distance target. In this paper, the basic algorithm of low resolution radar CFAR detection is introduced, and the performance of the algorithm is analyzed. Three CFAR detection algorithms for extended range targets are proposed. It is verified that the multichannel detection algorithm based on sequential statistics has the best detection performance under the background of logarithmic normal clutter. Based on the analysis of many CFAR detection algorithms, Cell average CFAR detection algorithm with optimal performance under low resolution radar and multichannel detection algorithm based on sequence statistics with optimal performance under high resolution radar are applied to FPGA (Field-Programmable Gate Array) engineering). FPGA As an emerging signal processing element, High integration, high speed, high reliability and stability, can complete complex timing design. Based on the advantages of parallel processing of FPGA, this paper analyzes the characteristics of two CFAR detection algorithms applied to different objects, reasonably allocates resources and synthetically considers the factors of data volume and running speed, and completes the engineering design of the algorithm. Finally, the image splicing algorithm and the CFAR detection algorithm are summarized, and the data processing process from imaging to detection of step frequency signal is completed.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN957.51

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