复合高斯杂波中MIMO雷达DOA估计的克拉美-罗下限

该文研究了复合高斯杂波下MIMO雷达DOA估计的平均克拉美-罗下限(Average CRB, ACRB)。首先,给出了MIMO雷达信号与杂波模型;然后,推导出目标DOA估计ACRB的一般关系式,在此基础上给出当杂波texture分量满足反Gamma分布时,ACRB的闭合表达式;接着,研究了目标DOA估计的中断CRB(Outage CRB),克服了一个发射单元时ACRB发散的问题;最后进行计算机仿真并给出结论。结果表明MIMO雷达的空间分集能有效地降低其DOA估计ACRB,且ACRB随发射单元数量的提高而减小;另外在相同条件下,MIMO雷达在复合高斯背景下DOA估计的ACRB大于相应高斯背景下的ACRB。     

The Rao and Wald Tests Designed for Distributed Targets with Polarization MIMO Radar in Compound-Gaussian Clutter

In high resolution radars, the distributed target is usually modeled as a few isolated points referred to multiple dominant scattering centers, while the clutter is a compound-Gaussian model. Additionally, the polarimetric diversity can be exploited to enhance detection performance. Motivated by extending the detection problem of multiple-input multiple-output (MIMO) radar to such cases, this paper mainly addresses distributed targets detection problem with polarization MIMO radar against a compound-Gaussian clutter dominated scenario with unknown covariance matrix. The adaptive detectors based on Rao and Wald criteria are studied, and a two-step design procedure is adopted. Specifically, the Rao and Wald tests are derived by assuming a known covariance matrix, and then a suitable estimation of the covariance matrix based on the secondary data is inserted into the derived detectors to make them fully adaptive. Some numerical results are presented together with a polarization generalized likelihood ratio test (GLRT), showing that the derived detectors provide excellent detection performance in spiky clutter for distributed targets, and that the polarimetric diversity can be exploited to improve detection performance. Overall, the Wald test performs the best.     

MIMO Radar Moving Target Detection Against Compound-Gaussian Clutter

This paper focuses on the moving target detection (MTD) problem for multiple-input multiple-output (MIMO) radar in the presence of compound-Gaussian clutter. By exploiting the spatial and velocity diversities, we devise two different generalized likelihood ratio tests (GLRTs) according to the centralized and distributed processing schemes of MIMO radar systems, respectively. Then, we investigate the fully adaptive detectors, where the covariance matrix is replaced by a suitable estimator based on the secondary data. Finally, we provide several numerical simulations with typical parameters, and the results illustrate that the newly proposed detectors can provide much better detection performance in spikier clutter for moving targets than the phased-array counterpart and those obtained in Gaussian environment.     

MIMO Radar with Colocated Antennas

We have provided a review of some recent results on the emerging technology of MIMO radar with colocated antennas. We have shown that the waveform diversity offered by such a MIMO radar system enables significant superiority over its phased-array counterpart, including much improved parameter identifiability, direct applicability of adaptive techniques for parameter estimation, as well as superior flexibility of transmit beampattern designs. We hope that this overview of our recent results on the MIMO radar, along with the related results obtained by our colleagues, will stimulate the interest deserved by this topic in both academia and government agencies as well as industry.     

载波频率偏移下分布式MIMO系统性能分析

文中针对载波频率偏移对分布式MIMO系统的性能进行了仿真分析,仿真结果表明：载波频率偏移和不理想的信道估计会对系统性能产生较大影响;高阶调制更容易受到载波频率偏移的影响;ZF和MMSE译码算法与传统的Alamouti译码算法相比对于载波频率偏移更加稳健,当｜w-2-w-1｜取值较大时,采用ZF和MMSE译码性能要好于传统的Alamouti译码算法;随着各链路载波频率偏移差别｜w-2-w-1｜的减小,传统的Alamouti译码算法性能不断改善。     

复合高斯杂波协方差矩阵估计的失配性能分析

在球不变随机向量的复合高斯杂波满足局部均匀的背景下,当估计的杂波分组大小与实际情况失配时,分析了自适应归一化匹配滤波器(ANMF)的恒虚警率(CFAR)特性和检测性能.理论分析表明,当杂波实际分组大小是估计分组大小的整数倍时,ANMF检测器对协方差矩阵结构和杂波功率水平均具有CFAR特性;而在其它的情况下ANMF检测器...     

复合高斯海杂波环境下雷达虚警概率分析

针对在服从复合高斯分布的海杂波条件下,进行脉冲积累检测的非相干处理雷达,推导出了其检测变量因子的概率密度函数。由于复合高斯海杂波的分布形式较为复杂,导致直接求解其概率密度困难。为了在数学上获得上述条件下雷达系统的理论性能,文中借助一种基于矩生成函数的近似方法,得到了检测变量因子概率密度的高精度解析结果。经过仿真分析,结果表明该近似方法的精确性很高,并且可以方便地推导出雷达虚警概率等性能的解析结论。     

阵元幅相误差对AEW雷达二维杂波谱的影响

本文研究了不可避免的阵元幅相误差对各列先微波合成为列子的矩形侧面相控机载预警（ＡＥＷ）雷达二维杂波谱的影响，并分析了基于理想“脊背型”杂波谱的二维信号处理性能下降的原因，为深入研究时空二维处理提供了基础。     

机载雷达极化空时联合域杂波抑制性能分析

针对当前机载雷达面临强杂波抑制和微弱目标检测等难点问题,提出了一种极化空时联合处理新方法.该方法充分利用了目标与杂波在极化域、空域和时域(Doppler域)的特征差异,提高了抑制杂波、增强目标的能力.本文首先建立了机载极化阵列雷达接收信号模型和滤波算法模型.其次,利用分辨格思想及特征值、特征向量和功率谱的关系,构建了完全极化情况下杂波协方差矩阵新的等价关系.在此基础上,详细推导了新方法的杂波抑制性能,得到了输出信干噪比(SINR)与空间匹配系数,Doppler匹配系数,极化匹配系数,杂波脊斜率,信噪比(SNR),杂噪比(CNR)等的定量解析表达式.并与空时自适应处理(STAP)进行比较,从理论上分析得到了极化空时处理性能优于空时处理.特别在检测慢速运动目标时,新方法具有较强的稳健性.最后,仿真算例验证了模型的正确性.     

复合高斯杂波下的3种目标检测算法研究

针对复合高斯分布背景下的慢速目标检测问题,从贝叶斯统计检测理论出发,系统分析了最优的GLRT检测算法、次优的基于AR模型的目标检测算法和传统的自适应MTI检测算法。结合这3种算法的特点阐述了它们的检测性能和工程可实现性。并在最后通过IPIX雷达实测海杂波数据对上述结论进行了验证,实验结果表明在性能损失不大时,基于AR模型的目标检测算法易于工程实现。     

复合高斯杂波中相干雷达极化自适应检测算法研究

研究了在复合高斯杂波中相干雷达极化自适应检测问题,基于广义似然比检验提出了一种新的检测算法。该算法关于杂波的结构分量统计特性有恒虚警的性质,敏感度分析表明虚警概率仅轻微地受到杂波相关特性变化的影响。仿真分析了不同状态时该算法的检测性能。结果表明该算法与先前的基于广义似然比的极化自适应检测算法检测性能接近,计算复杂度较低,有实际应用价值。     

分布式雷达相参发射原理与性能分析

通过调整空间距离较远的雷达发射天线的发射时间和初始相位可控制电磁波能量在空间的分布来增强感兴趣空间区域的信号能量。该文分析分布式雷达相参发射的原理,给出形成干涉峰点的条件,定义空间干涉能量分布函数来反映发射信号能量较平均能量的增益,其最大值为发射天线个数。在远场和近场条件下分析信号空间能量分布的特点,表明它在远场近天线距离呈条纹状,在近场远天线距离呈类晶体结构或独峰结构。为了让目标在干涉峰点内部,分布式相参发射在低频率、小目标的跟踪状态更有效。     

基于复合高斯杂波纹理结构的相干检测

传统的自适应检测器大多是在独立同分布纹理的前提下推导出的。然而,实测海杂波数据中各个距离单元的纹理具有相关性。该文将这一纹理相关性的信息加入到似然比检测中,提出一种基于纹理结构的相干检测器。基于涌浪调制在距离上产生纹理相关性的先验知识,确定与待检测单元纹理相关的距离单元数目,据此可以提供待测单元的纹理信息。实测数据实验表明,该检测器相对于逆伽马纹理复合高斯杂波下最优检测器具有一定的性能提升。     

严重拖尾复合高斯杂波中目标的自适应极化检测

该文研究极化高分辨雷达在动态变化的杂波场景中自适应检测小目标的问题。将统计特性严重拖尾的杂波建模为纹理分量为逆伽马分布的复合高斯过程,借助于广义似然比检验和辅助数据得到了自适应极化检测器,并推导了该检测器的虚警概率表达式,证明了该检测器对协方差矩阵结构具有恒虚警特性。最后,利用仿真杂波数据验证了检测器检测性能的有效性。     

机载分布式相干MIMO雷达的杂波谱分析

以多载频矩形脉冲信号为发射信号,建立了机载分布式相干MIMO雷达的杂渡模型;给出了经典的杂波功率谱估计方法和杂波自由度估计规则;仿真分析了多载频频率步进和不同误差条件下的最小方差（MV,minimum variance）杂波谱和杂波特征谱.仿真及分析结果表明：机载分布式相干MIMO雷达的杂波具有空时二维斜对角分布特性;杂波起伏、载机偏航均会使杂波谱展宽及杂波自由度增大;多载频频率步进的增长导致杂波去相关.     

MIMO分布式天线系统中的延时失衡性能分析

在MIMO室内分布式天线系统中,由于馈线以及极化天线本身的差异会引入延时不平衡因素。针对MIMO系统,从理论上分析分布式天线系统中延时失衡对MIMO系统带来的影响。通过仿真,定量分析了MIMO上下行链路中,延时失衡对基带性能的不利影响。结果表明,上行链路性能对延时差异不敏感;对下行链路,在时延差异达到0.5 CP时,系统性能会有约2 dB损失;当延时差异达到0.75 CP时,性能下降达到8 dB。     

单脉冲测角技术在MIMO雷达不同布阵下的性能分析

本文研究了多输入多输出(MIMO)雷达系统波束形成和单脉冲测角问题。MIMO雷达利用分集技术,在发射端全向发射正交波形,在接收端利用DBF技术同时形成多个波束。本文推导不同接收方式下MIMO雷达波束的方向图函数,给出其半功率波束宽度计算公式。将数字单脉冲测角技术应用于MIMO雷达,通过不同布阵对测角精度进行分析,并与相控阵雷达测角性能进行比较。计算机仿真结果表明,在相同阵列情况下,MIMO雷达测角性能优于传统相控阵雷达。     

Maximum Likelihood Estimation of Compound-Gaussian Clutter and Target Parameters

Compound-Gaussian models are used in radar signal processing to describe heavy-tailed clutter distributions. The important problems in compound-Gaussian clutter modeling are choosing the texture distribution, and estimating its parameters. Many texture distributions have been studied, and their parameters are typically estimated using statistically suboptimal approaches. We develop maximum likelihood (ML) methods for jointly estimating the target and clutter parameters in compound-Gaussian clutter using radar array measurements. In particular, we estimate i) the complex target amplitudes, ii) a spatial and temporal covariance matrix of the speckle component, and iii) texture distribution parameters. Parameter-expanded expectation–maximization (PX-EM) algorithms are developed to compute the ML estimates of the unknown parameters. We also derived the CramÉr–Rao bounds (CRBs) and related bounds for these parameters. We first derive general CRB expressions under an arbitrary texture model then simplify them for specific texture distributions. We consider the widely used gamma texture model, and propose an inverse-gamma texture model, leading to a complex multivariate$t$clutter distribution and closed-form expressions of the CRB. We study the performance of the proposed methods via numerical simulations.     

机载MIMO 虚拟阵LFMCW 雷达杂波距离旁瓣性能分析

线性调频连续波(LFMCW)信号应用于机载虚拟阵多输入多输出(MIMO)雷达体制。二者的结合,一方面,可在较少阵元条件下,获得虚拟的宽口径,改善雷达的测角性能;另一方面,采用连续波体制,在相同峰值发射功率的条件下,可增大雷达的探测距离,弥补MIMO 雷达宽波束发射导致的威力下降。LFMCW 信号的匹配滤波输出拖尾较长,文中对由此产生的杂波距离旁瓣泄漏问题进行了建模与分析,结果表明:LFMCW 雷达系统与线性调频脉冲雷达系统具有相似的杂波距离旁瓣泄漏特性,数值仿真验证了此结果的正确性。另外,非自适应处理的仿真结果也表明对高速、小RCS 的目标,LFM鄄CW 信号具有更高的输出信杂噪比。     

基于MIMO雷达的相干分布式目标 参数估计Cramer-Rao下界

 本文研究了MIMO雷达对相干分布式目标参数估计的Cramer-Rao下界(CRB).首先,给出相干分布式目标的MIMO雷达信号模型,推导出目标参数估计CRB的一般关系式;然后,给出在一个分布式目标、点目标和目标部分信息已知等特殊情况下的CRB;其次,讨论了MIMO雷达CRB的性质;最后,进行计算机仿真试验,研究不同条件下的MIMO雷达性能.结果表明由于具有避免波束形状损失等优点,MIMO雷达对相干分布式目标的参数估计CRB性能优于普通相控阵雷达.本文的研究揭示了MIMO雷达的相干分布式目标参数估计性能.