【作者】 李军；

【导师】 王雪松；

【作者基本信息】 国防科学技术大学 ， 信息与通信工程， 2011， 博士

【摘要】 雷达目标检测是雷达信号处理研究领域的经典问题。传统的研究通常针对低分辨率雷达,将目标视为点目标。当目标尺寸大于雷达空间分辨率,即目标表现为扩展目标时,基于点目标假设的检测技术难以充分利用目标回波特性,获得最优检测性能。近年来,宽带雷达的广泛应用以及雷达应用领域的拓展对扩展目标检测器设计和检测器的稳健性、适应性提出了新的要求。论文面向扩展目标雷达探测的需求,以提高检测器的稳健性和适应性为目标,针对典型的应用场景,开展扩展目标的雷达检测新技术、新应用研究。在扩展目标雷达检测新技术方面,论文首先分析了扩展目标回波特性,建立了扩展目标回波模型;在此基础上,针对噪声、杂波背景中的扩展目标检测问题,研究了扩展目标的参量、非参量检测新技术。具体工作包括:·扩展目标回波特性及建模:建立了基于几何绕射理论的扩展目标散射中心回波模型;推导了典型扩展目标回波的幅度、极化分布;分别针对高速、低速扩展目标建立了频域、时域回波模型。·扩展目标的参量检测技术:设计并分析了五种不同目标先验信息(目标回波幅度、极化、相位以及目标散射中心分布等)条件下扩展目标的单脉冲参量检测器;提出了一种高效、稳健、实用的准最优多通道单脉冲极值检测器及其检测性能的高精度近似分析方法;针对低速扩展目标,设计并分析了具有时-频-空域和极化域联合处理结构的多脉冲参量检测器,基于此检测器提出并分析了均匀、非均匀目标多普勒谱条件下扩展目标的多脉冲极值检测器;针对高速扩展目标在雷达多脉冲观测期间容易发生跨距离单元走动的问题,提出并分析了基于keystone变换的多脉冲参量检测方法,显著改善了高速扩展目标的检测性能。·扩展目标的非参量检测技术:针对未知杂波环境下的点目标检测应用,提出了Blind-CFAR(恒虚警率)非参量检测器,分别设计并分析了基于Padé逼近方法、最大熵方法的两种Blind-CFAR检测方案;在此基础上,分别基于非相参积累、极值积累和二进制积累等脉冲积累方法,提出并分析了三种扩展目标Blind-CFAR检测器。上述Blind-CFAR检测器克服了现有CFAR检测器过度依赖于参量估计精度的缺点,可适用于多种类型杂波背景下的目标检测。在扩展目标检测器设计、分析的基础上,论文面向航空安全、反隐身等应用领域,研究了扩展目标检测技术在飞机尾流雷达探测中的新应用,分析了典型大气条件下飞机尾流的雷达可探测性。具体工作包括:·分析了晴空、降水条件下飞机尾流的电磁散射机理和雷达目标特性;分别基于飞机尾流雷达探测实验、理论分析,获得了晴空、降水条件下飞机尾流的RCS(雷达散射截面)和多普勒谱;建立了飞机尾流的雷达回波模型和检测模型,导出并分析了飞机尾流的局部最大势(LMP)检测器以及均匀、非均匀飞机尾流多普勒谱条件下的广义似然比检验(GLRT)检测器,为飞机尾流雷达探测提供了理论基础。·导出了晴空、降水条件下飞机尾流探测的雷达方程;分析了典型雷达系统的飞机尾流探测距离,并将其与隐身飞机探测距离进行了比较研究。研究结果表明,在降水条件下,飞机尾流探测距离可望大于隐身飞机探测距离。论文在目标检测方面的研究成果对宽带雷达和分布式雷达目标检测具有重要的理论意义,在飞机尾流检测方面的研究成果在航空安全、反隐身等应用领域具有很大的应用潜力。更多还原

【Abstract】 Radar target detection is a classic problem in the research area of radar signal pro-cessing. Traditional research is usually for low-resolution radars and treats the target asa point target. When the target’s dimensions are greater than the radar’s spatial resolu-tions, i.e., when the target is an extended target, the detection techniques based on theassumption of point targets are difficult to make full use of the characteristics of the tar-get’s echoes, and to obtain optimal detection performance. In recent years, the extensiveapplication of broadband radars and the expansion of radar application have brought upnew requirements for the design, robustness, and adaptability of extended target detectors.This dissertation, facing the requirements of the radar detection of extended targets andaimingtoimprovetherobustnessandadaptabilityofdetectors,studiesnewtechniquesandnewapplicationoftheradardetectionofextendedtargetsfortypicalapplicationscenarios.In the aspect of new techniques of the radar detection of extended targets, the char-acteristics of extended targets’echoes are analyzed, and some echo models of extendedtargets are established first. On this basis, for the problems of the detection of extendedtargets in noise, clutter backgrounds, new techniques of the parametric, nonparametricdetection of extended targets are studied. The work includes:·Characteristics and modeling of extended targets’echoes: An echo model based onthe geometrical theory of diffraction is established for the scattering centers of ex-tended targets. The distributions of the amplitudes and polarization of the echoes oftypical extended targets are deduced. A frequency-domain echo model and a time-domain echo model are established for high-speed and low-speed extended targets,respectively.·Parametric detection techniques of extended targets: Five single-pulse parametricdetectors are designed and analyzed for extended targets with different a priori infor-mation (amplitudes, polarization, and phases of the target’s echoes, and distributionsof the target’s scattering centers, etc.). A quasi-optimal multi-channel single-pulseextreme detector, which is efficient, robust, and practical, is proposed, and a high-precision approximate analysis method is proposed for its detection performanceanalysis. For low-speed extended targets, a multi-pulse parametric detector witha time-frequency-spatial and polarization domain joint processing structure is de-signed and analyzed. Based on this detector, some multi-pulse extreme detectors are proposed and analyzed for extended targets with homogeneous, non-homogeneousDoppler spectra. For the problem that a high-speed extended target is prone to crossone or more range cells during the period of the radar’s multi-pulse observation, amulti-pulse parametric detection method based on the keystone transform is pro-posed and analyzed, which can significantly improve the detection performance ofhigh-speed extended targets.·Nonparametric detection techniques of extended targets: For the detection of pointtargetsinunknownclutterenvironment,anonparametricdetectornamedBlind-CFAR(constantfalsealarmrate)detectorisproposed,andtwoBlind-CFARdetectionschemes,whicharebasedonthePadéapproximationmethodandthemaximumentropymethodrespectively, are designed and analyzed. On this basis, based on the pulse integra-tion methods of non-coherent integration, extreme integration and binary integra-tion, three Blind-CFAR detectors for extended targets are proposed and analyzed.The Blind-CFAR detectors have overcome the shortcoming of the existing CFARdetectors that they are over-relied on the accuracy of parameter estimation, and areapplicable to target detection in many types of clutter environment.Based on the design and analysis of the extended target detectors, new applicationof the extended target detection techniques in the radar detection of aircraft wake vorticesis studied, and the radar detectability of aircraft wake vortices under typical atmosphericconditions is analyzed for aviation safety, anti-stealth and other applications. The workincludes:·The electromagnetic scattering mechanism and radar target characteristics of aircraftwake vortices in clear and precipitation air are analyzed. The RCSs (radar cross sec-tions) and Doppler spectra of aircraft wake vortices in clear and precipitation air areobtained based on the radar detection experiments of aircraft wake vortices and the-oretical analysis respectively. An echo model and a detection model are establishedfor the radar detection of aircraft wake vortices. A locally most powerful (LMP)detector of aircraft wake vortices and two generalized likelihood ratio test (GLRT)detectors of aircraft wake vortices with homogeneous, non-homogeneous Dopplerspectra are deduced and analyzed, which provides a theoretical basis for the radardetection of aircraft wake vortices.·Radar equations for the detection of aircraft wake vortices in clear and precipitation air are deduced. The detection range of aircraft wake vortices with typical radarsystemsisanalyzed,andiscomparedwiththeradardetectionrangeofstealthaircraft.The results show that, under precipitation conditions, the detection range of aircraftwake vortices is expected to be greater than that of stealth aircraft.The results of this dissertation on target detection are of important theoretical signifi-cance for broadband and distributed radar target detection, and the results on the detectionof aircraft wake vortices are of great potential in aviation safety, anti-stealth and otherapplications.更多还原