Constant False Alarm Rate Acquisition Algorithm for Compass B1C Signal

In order to improve the sensitivity of the Compass B1C signal acquisition for the receiver,the principle of constant false alarm rate(CFAR)is applied for the B1C pilot channel acquisition to realize the dynamic adjustment of the threshold of acquisition against the carrier to noise ratio.The non-coherent data/pilot combined acquisition algorithm for B1C signal is analyzed to make full use of the power of the B1C signal under the condition of low carrier to noise ratio.On this basis,to improve the acquisition sensitivity of the receiver,the principle of constant false alarm probability is applied for the non-coherent data/pilot combined acquisition algorithm.Theoretical analysis and simulations show that the non-coherent data/pilot combined acquisition algorithm with CFAR improves the B1C signal acquisition sensitivity of the receiver significantly,and achieves a better Receiver Operating Characteristic compared with the traditional acquisition algorithms.

Performance of Order-statistics Constant-false-alarm-rate Detector with Noncoherent Integration and Its Application to OTH Radar

Noncoherent integration is often ed for approving performance in detection of radar signal. Order-statistics constant false alarm rate (OS-CFAR) detector has some advantages in clutter and multiple target situations. AnOS-CFAN detector with noncoherent integration after Square law envelope detector is presented and an analysis of detection performance for the chi-Square family of Swerling fluctuating targets is given. Its application to the high frequency(HF) ground wave over-the-horizon (OTH) radar is discussed as well.

A Double-threshold Constant False Alarm Rate Detector And Its Performance Analysis

he cell averaging and the order statistics are two typical algorithms for constant false alarm rate detector in radar system. They have different advantages in stationary noise background and fluctuation clutter environment respectively. This paper presents a doublethreshold constant false alarm rate detector constructed on the basis of synthesizing the advantages of the two algorithms above and avioding their disadvantages. The performance of the detector is analyzed, and the simulation result is given.

Frame Detection Based on Cyclic Autocorrelation and Constant False Alarm Rate in Burst Communication Systems

Frame detection is important in burst communication systems for its contribu- tions in frame synchronization. It locates the information bits in the received data stream at receivers. To realize frame detection in the presence of additive white Gaussian noise （AWGN） and frequency offset, a constant false alarm rate （CFAR） detector is proposed through exploitation of cyclic autocorrelation feature implied in the preamble. The frame detection can be achieved prior to bit timing recovery. The threshold setting is independent of the signal level and noise level by utilizing CFAR method. Mathematical expressions is derived in AWGN channel by considering the probability of false alarm and probability of detection, separately. Given the probability of false alarm, the mathematical relationship between the frame detection performance and EJNo of received signals is established. Ex- perimental results are also presented in accor- dance with analysis.

Solution of false alarm and slow response in flame detector

A new flame detector with one ultraviolet and two infrared detectors is designed. The ultraviolet detector is of rapid response(≤10 μs) while the two infrared detectors usually have a response time of more than 5 ms. The ultraviolet detector is applied to deal with the flame of large scales. When facing the flame of mid or small scales, the three detectors cooperate. Employing the high-order derivatives of the sample data of the infrared circuits to improve the sensitivity, the response speed is greatly improved. The data of the temperature sensor is used to adjust circuit parameters in real time, thus reducing the effect of temperature drift. The flame detectors are tested at different distances and the response time is as rapid as 0.65 ms. The test results show that the new flame detector has the characteristics of high speed and a low rate of false alarms.

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.

基于双边截断的双参数海上风电站SAR图像CFAR检测

文章提出了1种基于双边截断的双参数海上风电站SAR图像CFAR检测器DTCS-TPCFAR,目的是提高在具有多个目标海上区域和石油泄漏区域等环境下对海上风电站的检测性能。DTCS-TPCFAR所提出的双边截断杂波的方法,能够同时消除高强度和低强度异常值的干扰,同时保留真实的杂波样本。通过使用最大似然估计计算双边截断后样本的均值和标准差,然后通过这2个参数估计值计算出截断阈值,最后再结合指定的虚警率(Probability of False Alarm,PFA)来对测试单元(Test Cell,TC)进行判断,完成最终的目标检测。这也是首次将CFAR检测器用于检测海上风电站。文章通过Sentinel-1数据集来验证该方法的有效性。实验结果表明,文章所提出的算法在相同指定虚警率下,具有更高的检测率(Detection Rate,DR)和更低的误报率(False Alarm Rate,FAR)。

基于FAR和FRR融合的多模态生物特征识别

通过多生物特征识别融合可以显著地改善系统的识别性能,在多生物特征识别中,匹配分数级融合最常用.现有的匹配分数级融合策略包括基于归一化的融合、基于密度的融合和基于分类器的融合.本文分析了这三种融合策略的优缺点,结合分数归一化和基于密度方法的优点,提出了一种新的基于信任度的融合策略.其中,信任度是以错误拒绝率和错误接受率为基础,既避免了直接求取某个匹配分数的后验概率,又能够刻画匹配分数的分布.将本文方法与几种有代表性的方法进行实验比较,结果表明,这种新融合模式可以有效地改进多生物特征识别系统的性能.

机载监视雷达地杂波背景中的CFAR检测方法

在充分考虑了具体雷达体制和工作环境的基础上认为,采用二维有序统计恒虚警处理方法(2D OS CFAR)适合于机载监视雷达地杂波背景中的恒虚警概率(constantfalsealarmrate,CFAR)检测。同时,对该方法在不同杂波背景、不同窗口大小、不同干扰数目时的检测性能进行了理论分析和实验仿真。仿真结果表明,该方法能有效地提高机载监视雷达对地工作方式时的CFAR检测能力。

相参雷达时频域CFAR检测门限获取方法研究

相参雷达体制下采用时频域处理的CFAR检测器面临的一个共性问题就是由于时频域杂波模型与实际不匹配,以及数据样本有限导致的模型参数无法准确估计,进而导致实际检测器性能总是与理论设计有较大差距.为此,本文通过分析相参雷达时频域恒虚警(CFAR)检测门限与虚警概率的函数关系,提出一种基于最小二乘拟合的检测门限获取方法,并给出了其工程实现途径.最后,采用实测数据对该方法进行检测性能仿真实验,实验结果表明,提出的检测门限获取方法有效可行,具有很好的工程应用前景.

改进的SAR图像双参数CFAR舰船检测算法

双参数CFAR检测中设置了目标窗口、保护窗口和背景窗口3个窗口,并且窗口的大小,滑动步长都要进行经验训练得到,效率低,对距离很近的舰船SAR图像会产生漏检。针对这些不足,该文提出了一种改进的双参数CFAR检测算法,该算法只取目标窗口和背景窗口,通过把泄露到背景窗口中的舰船部分去除并对背景窗口中的剩余部分进行均值和方差估计来检测舰船,并且将窗口滑动步长取为目标窗口尺寸。相对双参数CFAR算法,结构得到了简化,检测结果的虚警率减小,对距离很近的舰船不会产生漏检,计算效率得到了改善。仿真结果表明了方法的有效性。

基于熵特征的DRFM有源欺骗干扰CFAR检测

基于数字射频存储(digital radio frequency memory,DRFM)技术的转发式干扰的存在性检测是对抗有源欺骗干扰的前提。干扰机的相位取样量化会导致干扰信号有谐波分量的寄生。在雷达距离/速度波门内同时存在目标信号和欺骗干扰信号的情形下,利用经验模态分解(empirical model decomposition,EMD)算法分离出干扰信号谐波分量,通过提取干扰谐波分量与目标回波在时频域上能量分布特征差异,提出了一种基于时频域熵特征的有源欺骗干扰检测方法。该方法不需要估计噪声参数,且具有恒虚警(constant false-alarm rate,CFAR)特性。蒙特卡罗仿真结果验证了该方法的有效性。

基于H-CFAR的SAR图像快速舰船目标检测

SAR舰船目标的快速、准确检测是SAR海洋业务化应用中的重要需求,文章提出了一种基于直方图恒虚警率(H-CFAR)的快速检测方法。该方法直接利用SAR图像的灰度直方图信息,并结合CFAR算法,实现了SAR舰船目标的检测;利用ASAR、TerraSAR和Radarsat-2数据对此方法进行了检验,结果表明,该方法与现有的K-CFAR相比,在相同的硬件条件下,能够更快更准确地实现SAR舰船目标检测。

SIRV杂波下距离扩展目标CFAR检测器

在球不变随机向量(SIRV,Spherically Invariant Random Vector)的非高斯杂波背景下,提出了一种新的距离扩展目标检测器.给出了检测参数的简易确定方法,推导了虚警概率与检测阈值的解析表达式,证明了所提检测器的恒虚警率特性.仿真实验表明,在参数设置合理情况下,所提出的检测器性能远好于已有的两种距离扩展目标检测器.另外,随着阵元数、目标散射点个数及杂波尖峰的增加,检测器的性能得到提高;且该检测器对第三门限的选取和不同的杂波相关性均具有很好的鲁棒性.

OSGO-和OSSO-CFAR在K分布杂波背景下的性能分析

该文证明了形状因子已知条件下OSGO-CFAR和OSSO-CFAR检测器在均匀统计独立的K分布杂波背景下具有恒虚警性能,分析了两种检测器在均匀杂波背景、杂波边缘和存在强干扰目标情况下的检测性能。并与OS-CFAR进行了比较,结果表明OSGO-CFAR在均匀杂波背景和存在强干扰目标情况下带来的附加检测损失很小, 在杂波边缘具有更好的虚警控制能力。所以,OSGO-CFAR是K分布杂波背景下一种性能比较好的恒虚警检测器。

间歇采样转发假目标对CFAR检测影响分析

分析间歇采样转发形成的假目标干扰对雷达CFAR检测的影响和间歇采样转发假目标生成机理,给出间歇采样转发假目标产生方法。在此基础上,以雷达一次搜索周期内虚警、漏警造成的检测代价作为检测性能指标,分别分析单元平均恒虚警检测器、有序恒虚警检测器、剔除和平均恒虚警检测器在间歇采样转发假目标干扰下的检测代价。着重分析间歇采样转发干扰关键参数对检测代价的影响。仿真结果表明,间歇采样转发产生的多个假目标显著提高了雷达的检测代价,检测代价受转发占空比、转发功率的影响较大,而受转发频率影响较小。在三种恒虚警检测器的对比中,剔除和平均恒虚警检测器相对于另两种检测器的检测代价更大些。

SAR图像CFAR检测的快速算法综述

针对合成孔径雷达(Synthetic aperture radar,SAR)图像目标检测中恒虚警率(Constant false alarm rate,CFAR)算法的广泛应用,进行CFAR检测的快速算法分析具有重要研究价值.首先概述了当前国内外对SAR图像CFAR检测快速算法的研究现状;然后分别从快速预筛选和迭代计算方法两个方面对各类快速算法的实时性及性能进行了分析总结,给出了四种基本CFAR检测器的迭代计算公式,并提出了一种研究CFAR检测快速算法的基本框架,现有的快速算法均可纳入该理论框架予以分析;最后,以经典双参数CFAR检测算法为例,对该基本框架进行仿真实现和性能分析,验证了其可行性与检测性能.结果表明:新的CFAR检测快速算法基本框架充分融合了快速预筛选思想和迭代计算方法的优势,有效提高了CFAR算法在SAR图像检测应用中的执行效率.

分布式目标的子空间双门限GLRT CFAR检测

研究了分布式目标在球不变随机变量杂波中的检测问题,提出了一种具有恒虚警特性的双门限广义似然比检测器。分布式目标建模为子空间信号,在距离维和多普勒频率维同时扩展.第一门限的作用是筛选信杂比高的待检测距离单元.将选出的距离单元进行能量积累并与第二门限进行比较做出判决.假设杂波协方差矩阵已知,构造了双门限检测器,并通过推导检测器虚警概率说明其具有恒虚警特性.将基于辅助通道数据的杂波协方差矩阵的估计值替换假设已知的杂波协方差矩阵,得到一个自适应检测器.通过Monte Carlo仿真进行性能分析,说明检测器的有效性和鲁棒性.

分布式MIMO雷达双门限GLRT CFAR检测

在分布式多输入多输出雷达目标检测中,为降低融合中心与局部雷达站之间的数据传输率,提出了一种双门限广义似然比恒虚警率检测算法.首先对局部广义似然比检验统计量进行第一门限判断,将过门限的局部检验统计量传送给融合中心.然后在融合中心进行融合检测,与第二门限比较得到判决结果.推导了双门限广义似然比检测器的虚警概率闭式解.仿真结果表明,双门限广义似然比检测算法在降低数据传输率的同时能保证较好的检测性能.

基于动态有序矩阵的外辐射源雷达CFAR算法

外辐射源雷达采用不可控的第三方辐射源,其电磁传播条件复杂,尤其是在低空目标探测中,检测性能极大地受到杂波特性的影响,使得传统恒虚警算法性能明显下降。为了改善检测性能,该文提出一种基于雷达杂波空间划分的动态有序矩阵恒虚警检测算法(DOM-CFAR)。该算法将杂波空间从距离和多普勒维进行划分,构造为有序矩阵,再根据背景杂波变化进行动态极值替换、提取杂波估计中值用以计算检测阈值,从而使得检测算法阈值可动态适应杂波功率变化。仿真和实测结果表明,该算法可以在均匀杂波、多目标和杂波边缘等复杂情况下保持稳定的检测性能。