复合高斯杂波环境中分布性目标相干雷达恒虚警检测算法研究

本文研究了在未知统计特性的复合高斯杂波环境中对分布性目标检测的问题。利用Toeplitz矩阵的次对称性提出了一种新的杂波协方差矩阵结构的估计方法,并用此估计方法来实现基于广义似然比检验的恒虚警检测算法。该算法能够在不需要杂波功率谱密度对称的情况下作到对杂波的结构分量和协方差矩阵都有恒虚警的性质,而且该实现方法的检测性能优于先前提出的实现方法。     

Estimating random amplitude polynomial phase signals: acyclostationary approach

Modeling of a class of nonstationary signals with randomly time-varying amplitude and parametric polynomial phase is addressed. A novel approach is proposed for the estimation of the time-varying phase by exploiting the higher order cyclostationarity of these signals. The method does not require nonlinear search, is easy to implement, and yields consistent estimates for the parameters. The resulting algorithms are theoretically tolerant to a large class of noises including additive stationary non-Gaussian noise and any Gaussian noise. Simulation examples supporting the theory are provided     

复合高斯杂波中自适应目标检测算法

本文研究了复合高斯杂波中已知给定距离-多普勒单元多普勒频率、未知目标幅度的自适应检测目标的问题。杂波散斑分量用未知自回归系数的自回归过程建模表示,通过求解自回归系数和目标幅度的最大似然估计,推导得到复合高斯杂波中的广义似然比检测器。在目标信号向量维数很大的情况下,该检测器对激励信号方差与纹理分量的乘积具有恒虚警率特性。数值仿真表明该检测器性能优于正则化自适应匹配滤波器。最后分析了目标信号向量维数、自回归模型阶数在不同信杂比下对检测器性能的影响。      

复合高斯杂波中距离扩展目标的参数化Wald检测

本文研究复合高斯杂波环境中的距离扩展目标的自适应检测问题。有色杂波采用参数未知的自回归（AR）过程描述。结合Wald检测准则,仅需对H1假设条件下的未知参数进行最大似然估计,给出了一种新的基于参数化模型的扩展目标检测器——参数化Wald检测器。该检测器的检验统计量可解释为首先针对各个待测单元分别计算检验统计量,然后将所有待测单元的输出进行非相参累加,其对杂波的随机功率起伏具有恒虚警率(CFAR)特性。相比于常规的基于协方差矩阵的检测方法,参数化检测算法的执行过程不需要依赖辅助数据,仅利用待测扩展目标数据即可实现自适应处理,有效缓解了训练压力并降低了计算量。仿真实验表明,所提出的参数化Wald检测器的检测性能优于之前提出的参数化广义似然比检测器的性能。      

对雷达杂波拖尾参数的提取

在传统的雷达杂波幅度分布参数的提取中，一直将整个杂波分布区域作为研究的对象，而实际感兴趣的区域在于大的杂波区域，即杂波拖尾区域。文中尝试提出了一种改进的方法，即只对拖尾区域作参数提取，仿真结果初步表明了该方法的有效性。     

用SAR原始数据对雷达脉冲信号失真的校正

该文提出了一种对雷达发射脉冲进行相位估计的算法。该算法利用Chirp Scaling原理对SAR信号进行距离迁移校正,但仅在方位向波束锐化,然后利用自聚焦的方法(Map Drift,PGA),在距离向进行自聚焦处理,提取距离向的相位误差信息。文中分析了影响相位估计精度的各种因素,并在算法中加入了迭代补偿方法,仿真结果验证了算法的正确性。     

复合高斯杂波加热噪声中基于Rao检验的分布式目标检测

随着雷达分辨率的不断提高,每个距离单元中分布的杂波能量逐渐减少,当杂噪比低于10dB时,热噪声对检测性能的影响是不可以忽略的。针对低杂噪比的情况,在复合高斯杂波加热噪声的背景中研究了分布式目标的检测问题。首先假设内部热噪声和外部杂波统计独立,在给定杂波纹理分量τ的前提下,将白高斯热噪声加上由球不变随机向量表示的复合高斯杂波之后的总干扰近似等效处理成一个新的复合高斯杂波,只是将其参数做了适当调整。然后将分布式目标建模为在距离维和Doppler频率维同时扩展的子空间模型,基于Rao检验构造了N-Rao检测器。通过对N-Rao检测器虚警概率的计算表明,在不存在目标的假设下,虚警概率只由脉冲重复数N、分布式目标占据的实际距离单元数H、每个距离单元内目标散射点总数目Nt来决定,即N-RAO检测器具有恒虚警率特性。最后通过Monte Carlo仿真实验表明,杂波形状参数v的减少与CNR的增加都会使N-RAO检测器的检测性能有所提高,且在低杂噪比的情况下,N-RAO检测器有很好的检测性能。      

Performance analysis of GLRT-based adaptive detector for distributed targets in compound-Gaussian clutter

The problem of adaptive detection for spatially distributed targets in compound-Gaussian clutter is studied. We first derive the optimum NP detector and suboptimum two-step GLRT detector. For the two-step detection strategy, we also introduce three covariance matrix estimation strategies and evaluate their CFAR properties and complexity issues. Next, the numerical results are presented by means of Monte Carlo simulation strategy. In particular, the simulation results highlight that the performance loss due to adaptively estimating the texture is negligible, and that the loss due to adaptively estimating covariance matrix largely depends on the estimation algorithm, the number of the secondary data vectors and the number of the scatterers.     

Suppression of radar clutter and multipath effects for wide-band signals (Corresp.)

Methods for narrow-band clutter suppression are examined to determine their applicability to wide-band signal analysis. Algorithms amenable to wide-band theory are established, and a simple example is given.     

Adaptive clutter suppression based on iterative adaptive approach for airborne radar

To improve the performance of the recently developed weighted least-squares-based iterative adaptive approach (IAA) in space–time adaptive processing (STAP) for weak or slow targets detection, we propose a novel IAA scheme to adaptively suppress the ground clutter by using the secondary training data (STD). Especially, we use the IAA to estimate the clutter plus noise covariance matrix from a very small number of STD. The resulting clutter plus noise covariance matrix can be utilized to form the STAP filter and then suppress the clutter. To reduce the computational complexity of the IAA, we exploit the sparsity of large clutter components in the angle-Doppler image and develop a modified IAA algorithm employing a soft-thresholding to adaptively determine the entries of each iteration that should be updated. Simulation results show that our proposed scheme outperforms the conventional IAA scheme over weak or slow targets detection and the modified IAA algorithm exhibits a comparable or even a better performance than the IAA algorithm but a lower computational complexity.     

Optimum radar signal processing in clutter

This paper considers the joint optimization of a class of radar signals and filters in a number of clutter-pins-noise environments. The radar signal processor in this case will be optimum in the sense that its output at the time of target detection yields the maximum ratio of peak signal power to total interference power. If the interference at the input to this signal processor is a Gaussian random process, this processor also yields the maximum probability of detection for a given value of false-alarm probability. The signals used are pulse trains and the filters are tapped delay lines. The purpose of signal design is to determine the optimum complex weighting for each pulse of the pulse train. Filter design yields the optimum complex weighting for the output taps of the delay line. Filter design for a specified signal is considered first. This is followed by combined signal and filter design and matched filter design. Constrained signal and filter design is investigated last. It should be emphasized that the optimizations require a knowledge of the clutter time-frequency distribution. For practical situations, when the clutter distribution is unknown, an adaptive filter is proposed that automatically provides the optimum filter weights for a given transmitted signal. When the clutter has a range-time extent less than the equivalent range-time extent of the signal, filter design alone yields nearly optimum performance. As the clutter becomes extended in range-time, it is necessary to consider jointly the design of signal and filter to obtain an optimum radar signal processor. In this report it is suggested that the signal be designed under the assumption of the clutter being extended over a broad range of Dopplers and that the signal processor consist of a bank of adaptive filters. Then each filter output yields the maximum ratio of peak signal to total interference power for this signal design.     

An approach to suppress short-range clutter for non-side looking airborne radar

When the Airborne Early Warning (AEW) radar transmits medial or high Pulse Repetitive Frequency (PRF) signal, the range ambiguity occurs. The clutter of short-range clutter has serious range dependence problem for non-Side Looking Airborne Radar (non-SLAR). As a result, the clutter plus noise covariance matrix can not be estimated correctly, and the performance of clutter suppression obtained by Space-Time Adaptive Processing (STAP) degrades greatly. The uniform linear array has not elevation degrees; therefore, the short-range clutter can not be suppressed directly. A short-range clutter suppression method is proposed. The method first estimate the elevation angles of the am-biguous short-range gate, then eliminates short-range clutter by space time interpolation and adds moving target protection in the procedure. This method can suppress the short-range clutter well. Simulation results show the validity of the method.     

Maximum-entropy spectral analysis of radar clutter

The paper reviews a processor that uses the maximum-entropy spectral estimate to provide a set of Doppler-based features for classifying the different forms of radar clutter as encountered in an air traffic control environment. This enables vectoring aircraft around an area that is made hazardous by the presence of major weather disturbances or migrating flocks of birds. An overview is given of experimental results that demonstrate the practical viability of this Doppler processor.     

An experimental classification of radar clutter

This letter describes some experimental results concerning the classification of radar clutter-according to whether it is due to reflections from ground, weather disturbances, or migrating flocks of birds. The procedure is based on the maximum entropy method.     

Iterative parameter estimation of multiple chirp signals

The authors propose an algorithm for estimating the parameters of multiple superimposed chirp signals in additive white noise. The algorithm is based on a novel iterative approach that significantly reduces the error propagation effect inherent in many existing techniques. Moreover, it allows the estimation over a wider range of phase parameter values while still maintaining a better estimation accuracy     

雷达杂波自适应抑制技术

从杂波特性入手,讨论了对运动杂波进行自适应抑制的必要性。理论分析了杂波自适应抑制技术,并进行了仿真验证。针对工程实际中多普勒频率估计不够精确的情况,提出在杂波多普勒频率粗估计的基础上采用多个自适应滤波器,根据输出功率比较确定最佳杂波抑制滤波器,大大提高了系统性能,并且不需要很大的设备量。     

Analysis of sea spikes in radar sea clutter data

In this paper three sets of high-resolution, coherent, and polarimetric radar sea clutter data are analyzed and compared with radar sea clutter models. The nature of the data allows a thorough analysis of the power, polarization and velocity of the sea clutter. It is shown that these quantities, especially the velocity, are good measures of many physical properties of the ocean surface. Furthermore, it is shown that these physical properties match well with the sea clutter models. Sea clutter is found to consist of two components, a diffuse background, characterized by low values of backscattered power, HH/VV polarization ratio and Doppler velocity, and a number of spiking events, which possess higher power, polarization ratio and velocity. The background is reasonably well modeled by tilt-modulated Bragg scattering, whereas the spikes may be associated with the scattering on steepened and/or breaking waves. Moreover, it is shown that the influence of microbreakers has to be taken into account to explain the relatively high polarization ratio. A breaking wave origin for the spikes is supported in two ways. First, by a detailed analysis of the temporal behavior of individual spike backscatter properties, and second, by a statistical analysis of the entire population of spikes.     

Classification of radar clutter in an air traffic controlenvironment

The results of an experimental study aimed at the classification of radar clutter encountered on ground-based coherent scanning radar systems used for air traffic control are presented. The clutter signals of interest are primarily those due to birds and to clouds and weather systems. A historical perspective on the radar clutter classification problem is given, and related issues are discussed. The important features of radar as a sensor in an air traffic control environment are described, and physical phenomena in radar clutter and targets, which provide the physical basis for the discrimination between the different radar clutter classes, are discussed. The feature of selection/extraction procedure, which is based on the multisegment Burg algorithm, is described. The experimental evaluation of a parametric Bayes classifier and a neural network classifier is reported     

Improved estimation of hyperbolic frequency modulated chirp signals

This article deals with parameter estimation of product signals consisting of hyperbolic FM and chirp factors. A computationally simple algorithm that decouples estimation of the chirp parameters from those of the hyperbolic FM part is presented. It relies on a simple data transformation that removes the hyperbolic FM component, leaving one with the simpler problem of estimating chirp parameters. For the latter, the high-order ambiguity function (HAF) is adopted. Schemes for estimating the hyperbolic FM parameter are also proposed. The method improves on existing approaches and is shown to provide performance close to the Cramer-Rao bound     

基于正负斜率线性调频脉冲信号的一种新的测速方法

提出了一种基于正负斜率线性调频脉冲信号进行目标测速的方法,通过分析两次MTD后的距离维信息和多普勒维信息,分别对速度进行了初步估计和精确测量.综合两次MTD结果得到了目标的实际速度,并推导出了脉冲占空比和速度测量误差的关系式.仿真表明了此方法的正确性,且具有一定的应用价值.