Method of moving target detection based on sub-image cancellation for single-antenna airborne synthetic aperture radar

The method of moving target detection based on subimage cancellation for single-antenna airborne SAR is presented. First the subimage is obtained through frequency processing is pointed out. The imaging difference of a stationary objects and moving object in the subimage based on the frequency division is analyzed from the fundamental principle. Then the developed method combines the shear averaging algorithm to focus on the moving target in the subimage, after the clutter suppression and the focusing position in each subimage is obtained. Next the observation model and the relative movement of the moving targets between the subimages estimate the moving targets. The theoretical analysis and simulation results demonstrate that the method is effective and can not only detect the moving targets, but also estimate their motion parameters precisely.

A PARAMETER ESTIMATION FOR DETECTION AND IMAGING OF MOVING TARGETS WITH SAR BY WVD

Based on a joint time-frequency two dimensional processing, this paper proposes a method for the detection and imaging of moving targets SAR by using Wigner-Ville Distribution (WVD). It is a parameter estimation method to generate a high resolution image. The problem of WVD in dealing with multi-point targets and extended targets are also discussed. The computer simulation results illustrate its availability.

RADAR HRR PROFILING FOR GROUND MOVING TARGET USING PHASE-CODED AND HOPPED-FREQUENCY WAVEFORMS

To obtain the radar High Range Resolution (HRR) profile of the slowly moving ground target in strong clutter background, the Phase-Coded Hopped-Frequency (PCHF) waveform is proposed. By multiple-bursts coherent processing, the HRR profile synthesis, target velocity compensation and clutter compression can be accomplished simultaneously. The new waveform is shown to have good ability to suppress ground clutter and good Electronic Counter-CounterMeasures (ECCM) ability as well. The clutter compression performance of the proposed method is verified by the numerical results.

New CFAR target detector for SAR images based on kernel density estimation and mean square error distance

A new constant false alarm rate （CFAR） target detector for synthetic aperture radar （SAR） images is developed. For each pixel under test, both the local probability density function （PDF） of the pixel and the clutter PDF in the reference window are estimated by the non-parametric density estimation. The target detector is defined as the mean square error （MSE） distance between the two PDFs. The CFAR detection in SAR images having multiplicative noise is achieved by adaptive kernel bandwidth proportional to the clutter level. In addition, for obtaining a threshold with respect to a given probability of false alarm （PFA）, an unsupervised null distribution fitting method with outlier rejection is proposed. The effectiveness of the proposed target detector is demonstrated by the experiment result using the RADATSAT-2 SAR image.

METHOD OF MULTI-TARGET TRACKING IN WIDE AREA SURVEILLANCE AIRBORNE RADAR SYSTEM BASING ON CLUSTERING ANALYSIS

This paper proposed a robust method based on the definition of Mahalanobis distance to track ground moving target. The feature and the geometry of airborne ground moving target tracking systems are studied at first. Based on this feature, the assignment relation of time-nearby target is calculated via Mahalanobis distance, and then the corresponding transformation formula is deduced. The simulation results show the correctness and effectiveness of the proposed method.

SURVEILLANCE OF MOVING TARGET BEHIND PARTITIONS USING A UWB-TWDR

This paper firstly analyzes the property of the low frequency electromagnetic wave, which can penetrate many types of non-metallic materials, and the ability of Ultra-Wide Band (UWB) impulse signal which has high range resolution. Then the methods are discussed for conducting surveillance through walls, detecting and locating the moving persons behind the partitions. The schematic diagram of Through-Wall Detecting Radar (TWDR) and the models of moving target are shown and the principle of detecting the moving target is also provided with coherent superimposing technique on a range gate. Finally an algorithm for estimating the location of targets is given. The performance of TWDR is validated by the experiments of penetrating a wood block, a red brick wall and a reinforced concrete wall.

距离角度失配条件下的FDA-MIMO雷达运动目标检测算法

频控阵-多输入多输出(Frequency Diverse Array-Multiple Input Multiple Output,FDA-MIMO)雷达是一种新体制雷达,其发射频率分集特性带来了额外的距离维信息,然而采样误差同样带来了导向矢量失配的问题,不仅如此,角度误差的存在也会进一步加重导向矢量的失配,极大地影响检测器的检测性能。此外,目标速度过快也会对FDA-MIMO雷达的目标检测性能产生影响。速度带来的影响具体表现在两个方面:一方面会导致目标的距离走动,从而导致不同慢时间的回波包络不能对齐,无法相干积累;二是频率增量引起的多普勒扩展,使得不同发射通道的多普勒频率不一样,这会进一步影响检测性能。针对上述问题,本文针对运动目标情况下的目标检测问题进行研究,为了解决目标运动带来的距离徙动和多普勒扩展效应,引入Keystone变换进行校正。此外,为了提升阵列失配条件下的目标检测性能,本文引入子空间模型,提出了距离角度失配情况下的子空间构建方法,并基于广义似然比检验(Generalized Likelihood Ratio Test,GLRT)准则推导了FDA-MIMO雷达在距离和角度失配条件下的自适应检测器。仿真结果表明:在高斯白噪声背景下,所提算法可以校正运动目标在速度较快情况下导致的距离徙动和多普勒扩展效应,且在阵列距离和角度失配条件下的检测性能优于传统的GLRT检测器。此外本文所提Keystone-空域处理检测器与Keystone-全空时处理检测器的性能接近,且计算复杂度更低。

Switching variability index based multiple strategy CFAR detector

A switching variability index （SVl） constant false alarm rate （CFAR） detector is proposed for improving the detection performance of VI-CFAR detectors in multiple targets backgrounds. When the presence of non-homogeneity in CFAR reference windows is indicated by a VI-CFAR detector, a switching- CFAR detector is introduced to optimize the performance of the VI-CFAR detector in homogeneous, multiple targets and clutter edge backgrounds. The structure and parameters selection method of the SVI-CFAR detector is presented. Comparisons with classic CFAR detectors and recently proposed detectors are also given. Theoretical analysis and simulation results show that SVICFAR detector maintains the good performance of the VI-CFAR detector in homogeneous and clutter edge backgrounds, while greatly improving the capacity of anti-multi targets.

基于等分剔除的毫米波雷达恒虚警检测研究

为解决车载毫米波雷达目标检测过程中在相邻多目标情况下会提高检测门限值,从而导致目标遮蔽现象,引发传统恒虚警(constant false alarm rate, CFAR)检测在多目标环境下产生漏检的问题,提出一种等分剔除恒虚警检测算法(equipartition deletion CFAR,ED-CFAR)。通过将目标两侧的参考单元等分取平均值得到子参考单元,对大于所有参考单元平均值的部分进行处理后排序,剔除部分较大子参考单元,计算得到门限值,与目标的信号幅度进行比较判断目标是否存在。仿真结果表明,在多目标检测的仿真场景下,信噪比为10 dB时,ED-CFAR算法的检测概率比单元平均恒虚警(CA-CFAR)算法提高0.39,比筛选平均恒虚警(CMLD-CFAR)算法提高了0.08,有效解决了传统均值类恒虚警检测在相邻多目标条件下的遮蔽问题。

基于多普勒偏移补偿的非线性FDA-MIMO雷达运动目标检测算法

非线性频控阵-多输入多输出(Frequency Diverse Array-Multiple Input Multiple Output,FDA-MIMO)雷达具有非线性增加的阵元频偏,使得雷达的距离-角度波束图不再呈现“S”型,而聚焦为点波束,以此将发射能量聚焦到目标位置能够获得更优异的目标检测性能。不过,FDA-MIMO雷达检测运动目标时,由于发射阵元间的频偏与目标速度存在耦合,导致在慢时间维出现多普勒偏移。基于插值滤波的重采样算法能够补偿阵元频偏带来的多普勒偏移,但对于非线性FDA-MIMO雷达,由于阵元间频偏不再是线性变化,上述算法将会失效。本文提出了一种新的算法,可以利用Keystone变换和多普勒偏移补偿的方法,来检测非线性FDA-MIMO雷达中的运动目标。建立了非线性FDA-MIMO雷达运动目标的回波模型,指出了基于插值滤波的重采样算法存在的不足,提出了一种基于速度搜索的算法来补偿非线性FDA-MIMO雷达检测运动目标时出现的多普勒偏移。首先利用Keystone变换消除目标回波的距离徙动,然后根据阵元间频偏构造多普勒补偿函数,利用多普勒补偿函数和各阵元脉压后的回波信号构造速度搜索函数,通过设定合适的速度搜索范围对其进行搜索,当该函数取得峰值时对应的速度即为真实速度,最后利用搜索的速度补偿多普勒偏移后再做相干积累检测目标。仿真结果表明:所提算法可以准确补偿阵元间的多普勒偏移,且在非线性FDA-MIMO雷达体制下的检测性能优于基于插值滤波的重采样算法。

Distribution-based CFAR detectors in SAR images

As traditional two-parameter constant false alarm rate （CFAR） target detec-tion algorithms in SAR images ignore target distribution, their performances are not the best or near best. As the resolution of SAR images increases, small targets present more pixels in SAR images. So the target distribution is of much significance. Distribution-based CFAR detection algorithm is presented. We unite the pixels around the test cell, and estimate the distribution of test cell by them. Generalized Likelihood Ratio Test （GLRT） is used to deduce the detectors. The performance of the distribution-based CFAR （DBCFAR） detectors is analyzed theoretically. False alarms of DBCFAR detection are fewer than those of CFAR at the same detection rate. Finally experiments are done and the results show the performance of DBCFAR is out of conventional CFAR. False alarms of DBCFAR detection are concentrated while those of CFAR detection are dispersive.

基于NSGA-Ⅲ的机载雷达空空射频隐身探测参数设计

目标探测任务要求雷达具备较大的发射功率,但这又会增大其辐射特征,从而降低射频(radio frequency,RF)隐身性能,因此如何权衡RF隐身与探测性能成为机载雷达RF隐身探测的难点问题。为此,本文提出一种用于机载雷达空中运动目标RF隐身探测的多目标优化参数设计方法。所提方法首先建立空中运动目标射频隐身探测多目标优化模型;然后利用非支配排序遗传算法Ⅲ(non-dominated sorting genetic algorithmⅢ,NSGA-Ⅲ)对该模型求解,获得帕累托最优解集;最后采用层次分析逼近理想解排序法对候选解集进行多属性决策获得最终方案。数值实验结果表明所提方法可有效应用于空中运动目标射频隐身探测参数设计。

动平台分布式雷达系统动目标低比特数据检测算法

动平台分布式雷达系统可有效提升系统的生存能力和探测性能,但运动平台之间通常采用无线传输方式,难以配备大通信带宽以传输完整的信号数据,给雷达系统的高性能检测带来极大挑战。由于低比特量化技术可显著降低分布式系统的通信传输代价和计算资源消耗,该文针对低信噪比弱信号环境下提出了动平台分布式雷达系统的低比特量化运动目标检测算法。首先,根据系统资源将各节点的多脉冲观测数据选择对应位数的低比特量化器进行量化,推导了关于量化器和多个目标状态的似然函数。其次,证明了低比特量化数据对应似然函数关于未知目标反射系数的凸性,并基于该特性设计了多普勒频移和反射系数的联合估计器。然后,针对探测区域中存在的多个状态未知目标设计了多目标检测器,推导了其恒虚警率门限。最后,通过推导系统的渐近性能设计了最优低比特量化器,在保证系统鲁棒性的同时有效提升了系统的检测性能。仿真实验分析了所提算法的检测与估计性能,结果证明了所提算法在低信噪比弱信号环境下的有效性,同时表明低比特量化数据可在仅占用低于20%通信带宽的基础上实现接近高精度(16比特量化)数据对应的检测和估计性能,且2比特量化策略可作为检测性能和雷达系统资源消耗的折中选择。

一种改进的高分辨率SAR图像超像素CFAR舰船检测算法

合成孔径雷达(SAR)图像舰船目标检测一直受到学者广泛关注,恒虚警率(CFAR)检测算法作为雷达图像经典目标检测算法被广泛应用于SAR图像舰船目标检测中。然而经典CFAR检测性能容易受到相干斑噪声影响,基于滑窗的检测结果对滑窗的尺寸选择非常敏感,难以保证杂波背景中不存在目标像素,并且计算效率较低。针对上述问题,该文提出了一种新的基于超像素无窗快速CFAR的SAR图像舰船目标检测算法。首先,利用基于密度的快速噪声空间聚类(DBSCAN)超像素生成方法生成SAR图像的超像素。在SAR数据服从混合瑞利分布的假设下,定义了超像素相异度。然后利用超像素精确估计每个像素的杂波参数,即使在多目标情况下,也可以克服传统CFAR滑动窗口的缺点。此外,基于SAR图像变异系数,提出了一种基于变异系数的局部超像素对比度来优化CFAR检测,以此消除大量杂波虚警,如陆地区域人造目标。对5幅SAR图像的实验结果表明,与其他方法相比,该文方法对不同场景SAR图像海面舰船目标检测都十分稳健。

基于时域弹跳射线法的海面复合目标近场回波仿真

雷达回波信号的获取对研究动态目标识别和雷达成像具有十分重要的意义。提出了一种基于时域弹跳射线法(Time Domain Shooting and Bouncing Ray, TDSBR)的动态目标回波仿真模型,用于模拟海上电大目标的近场雷达回波。该模型采用TDSBR方法直接在时域计算弹载雷达照射下的目标与海面近场复合散射特性,并结合“stop-go”方法模拟雷达与目标之间的相对运动,实现了弹载雷达照射下海上运动舰船目标的回波信号仿真。仿真结果表明,该模型可以有效呈现海面与海上目标的耦合效应,实现对目标速度和距离的预测,具有良好的精度和较高的效率,在海洋环境中弹载雷达的回波预测和目标检测中具有广阔的应用前景。

基于卷积神经网络的动目标检测

合成孔径雷达(SAR)动目标检测技术是雷达信号处理领域中的重要技术。文中利用深度学习高维特征提取能力,提出了一种基于卷积神经网络(CNN)的多通道SAR地面动目标检测算法,并针对雷达实测数据较少、动目标样本难以获得的问题,提出了基于仿真-实测混合样本集的网络训练方法完成网络的高精度训练。实测数据检测结果表明,此类方法能够有效地完成地面动目标检测,与传统动目标检测方法相比,具有显著的优势。

一种基于修正激活函数的CNN车载毫米波雷达目标检测方法

为了提高车载毫米波雷达在复杂城市道路环境中目标检测的抗杂波与干扰能力,本文利用卷积神经网络(CNN)特征参数提取和目标分类特性,提出了一种改进的基于CNN的车载毫米波雷达目标检测方法。该方法首先将毫米波雷达回波信号距离-多普勒二维数据运用滑窗进行分割,并采用CNN网络模型处理分割后的二维矩阵,训练二维CNN网络模型及其参数,使其具有提取回波特征并基于特征参数模型进行目标分类的能力,从而实现目标检测功能。通过对卷积神经网络模型结构进行优化,增加批量归一化层,优化Dropout层使得低权重特征失活,自适应地删减部分神经元节点修正该层非线性激活函数,进一步降低了CNN模型目标检测的虚警概率。实验结果表明,在相同虚警概率条件下,CNN网络检测方法目标发现概率优于传统的单元平均恒虚警检测方法,并且在低信噪比的条件下仍然能够保持较高的发现概率;在同等发现概率水平下,修正后CNN网络检测方法的虚警概率较修正前可提高约1个数量级。

一种高速可配置二维CFAR检测器设计实现

恒虚警率(constant false alarm rate,CFAR)检测是雷达在干扰背景下检测目标的重要自适应算法。二维CFAR算法随着参考窗口尺寸增大,运算量较大,仅靠软件实现并不能满足较高的实时性需求。文章基于现场可编程门阵列(field programmable gate array,FPGA)设计实现了一种兼容CA-CFAR、GO-CFAR、SO-CFAR和OS-CFAR 4种二维CFAR算法的硬件加速器,同时实现标称化因子、检测器类型、排序值K、参考窗口和保护窗口大小可配置的灵活性,对于256×2048点距离-多谱勒矩阵(Range Doppler Matrix,RDM)数据,4种检测器均可在2.71 ms内完成检测。设计采用全流水结构,具有高实时性。

基于截获因子评价的双基地面动目标指示LPI探测设计

电子战装备的无源探测对作战飞机的生存构成严重威胁。地面动目标指示作为机载雷达的重要功能,亟需提升其抗截获能力。结合双基雷达低截获特征,提出了基于截获因子评价的双基机载雷达地面动目标指示低截获探测设计方法。针对双基机载雷达地面动目标指示,简要分析了距离分辨率、最小可检测速度,推导了截获因子表达式,在满足探测性能前提下,设计了基于截获因子评价的低截获探测方法。仿真结果表明,所提出的方法能明显提升机载火控雷达地面动目标指示功能的抗截获性能。

基于SAR影像数据的多分辨率CFAR目标检测算法及精度分析

本文的研究目标是利用极化合成孔径雷达图像统计特性提高目标检测精度。从合成孔径雷达(SAR)成像机理出发,通过研究目标杂波的统计特性以及不同分辨率情况下人造目标的检测效果,探讨一种基于小波变换和恒虚警率(CFAR)的多分辨率算法进行目标检测的方法。实验分析比较传统CFAR目标检测算法与基于小波变换的多分辨率CFAR目标检测算法,实验结果表明,本文算法检测效果明显优于传统CFAR目标检测算法。