Multiband coherent radar detection against compound-Gaussianclutter

A Multiband GLRT-LQ (Generalized Likelihood Ratio Test-Linear Quadratic), MBGLRT-LQ, detector is derived for the coherent radar target detection against a compound-Gaussian clutter background. This scheme is an extension to the multiband case of the Asymptotically Optimum Detector (AOD), also derived under the name of GLRT-LQ in. The proposed multiband version of the algorithm shows two main advantages with respect to the original single-band algorithm. 1) For the adaptive implementation, it requires a much smaller area of homogeneous clutter echoes to estimate the covariance matrix of the interference; 2) it provides an optimum processing of the radar echoes when the radar operates in frequency agility, as electronic counter-countermeasure (ECCM) strategy. A closed form performance analysis is provided for the MBGLRT-LQ detector, which is used to compare it with the single-band version. An application to live recorded data is also presented to validate the obtained results     

不同机载电子干扰条件下的飞机敏感性模型

对典型作战场景中雷达制导导弹威胁下的飞机敏感性进行了研究,分别从导弹发射和命中2个方面,建立了远距离支援干扰(SOJ)和自卫干扰(SPJ)条件下的飞机敏感性模型。首先分析了在典型电子对抗措施(ECM)和电子抗干扰措施(ECCM)条件下的雷达探测距离;其次提出了用于评价欺骗干扰的有效时间模型,结合典型制导律,建立了不同干扰条件下导弹命中分析的仿真模型;最后对不同干扰条件下的飞机敏感性进行了仿真实验。结果表明:电子干扰一定程度上能够降低非隐身战机的敏感性,但是对于低雷达散射截面(RCS)或者采用先进抗干扰措施的武器系统而言,电子干扰对飞机敏感性降低的作用有限甚至有害。研究结果对现役飞机通过电子干扰降低敏感性以及对在研飞机的敏感性设计具有一定的参考意义。     

对SAR欺骗式干扰中差频补偿的研究

根据星载合成孔径雷达（SAR）的接收机工作原理提出一种欺骗式干扰方法，并分析了基准频率不一致这一因素对干扰效果的影响，提出了补偿措施，通过仿真验证了补偿效果。     

基于启发式自适应离散差分进化算法的多UCAV协同干扰空战决策

 研究了多无人作战飞机(UCAV)协同干扰空战决策(MUCJAD)问题,在干扰效能评估指标量化方法的基础上为该问题建立了优化模型。为有效求解该模型,提出一种启发式自适应离散差分进化(H-SDDE)算法。在H-SDDE算法中,设计了包含4种候选解产生策略的候选策略池,引入了候选解产生策略及其参数的自适应学习过程。此外,结合实际问题为算法设计了基于威胁度的扩展型整数编码方案、基于威胁度的启发式个体调整操作、基于约束满足的个体修复操作。在12个测试实例上进行了仿真验证,结果表明,H-SDDE算法与其他同类算法相比在求解质量和求解速度上具有明显优势,能够更好地发挥多UCAV协同干扰整体效果。     

Electronic warfare. [A century of powered flight: 1903-2003]

Electronic warfare (EW) is a term that includes a number of different electronic technologies for intelligence gathering and/or interfering with enemy operations. Electronic intelligence (ELINT), or eavesdropping, has been going on since the invention of the telephone and telegraph. Electronic countermeasures (ECM) deprive an enemy of the electronic spectrum by creating interference (jamming) that obscures their information or generates false information (spoofing). Electronic counter countermeasures (ECCM) is an effort designed to mitigate and overcome enemy ECM operations. ECM objectives include: search for signals in frequency, azimuth, and elevation; detect and identify radar signals via characteristics; and establish signal importance; commence appropriate countermeasures. It is only recently that these technologies have traditionally been categorized as EW, and are also referred to as electronic combat (EC). This section will focus on EW as it relates only to aviation.     

ECCM capabilities of an ultrawideband bandlimited random noise imaging radar

Investigated here is high-resolution imaging of targets in noisy or unfriendly radar environments through a simulation analysis of the ultrawideband (UWB) continuous-wave (CW) bandlimited random noise waveform. The linear FM chirp signal was selected as a benchmark radar waveform for comparison purposes. Simulation of the recovery of various types of target reflectivity functions (TRFs) for these waveforms were performed and analyzed. In addition, electronic counter-countermeasure (ECCM) capabilities for both types of systems were investigated. The results are compared using the error between the interference (jamming)-free recovered TRF and the recovered TRF under noisy conditions as a function of the signal-to-interference/jamming ratio (SIR/SJR). Our analysis shows that noise waveforms possess better jamming immunity (of the order of 5-10 dB improvement over the linear FM chirp) due to the unique radar correlation processing in the receiver.     

Adaptive digital beamforming for angle estimation in jamming

A radar digital beamforming (DBF) architecture and processing algorithm is described for nulling the signal from a mainlobe electronic jammer and multiple sidelobe electronic jammers while maintaining monopulse angle estimation accuracy on the target. The architecture consists of a sidelobe jamming (SLJ) cancelling adaptive array (AA) followed by a mainlobe jamming (MLJ) canceller. A mainlobe maintenance (MLM) technique or constrained adaptation during the sidelobe cancellation process is imposed so that the results of the SLJ cancellation process do not distort the subsequent mainlobe cancellation process. The SLJ signals and the MLJ signals are thus cancelled sequentially in separate processes. This technique was developed for improving radar processing in determining the angular location of a target, and specifically for improving the monopulse technique by maintaining the accuracy of the target echo monopulse ratio in the presence of electronic jamming by adaptive suppression of the jamming signals before forming the monopulse sum and difference beams     

Adaptive detection schemes in compound-Gaussian clutter

Radar detection of coherent pulse trains embedded in compound-Gaussian disturbance with partially known statistics is discussed. We first give a thorough derivation of two recently proposed adaptive detection structures. Next, we derive a different detection scheme exploiting the assumption that the clutter is wide-sense stationary. Resorting to the theory of circulant matrices, in fact, we demonstrate that the estimation of the structure of the clutter covariance matrix can be reduced to the estimation of its eigenvalues, which in turn can be (efficiently) done via fast Fourier transform codes. After a thorough performance assessment, mostly carried on via computer simulations, the results show that the newly proposed detector achieves better performance than the two previously introduced adaptive detectors. Moreover, a sensitivity analysis shows that, even though this detector does not strictly guarantee the constant false alarm rate property with respect to the clutter covariance matrix, it is robust, in the sense that its performance is only slightly affected by variations in the clutter temporal correlation     

网电空间数据链的认知抗干扰技术

为了增强复杂电磁环境中网电空间数据链的抗干扰能力,提出了基于发送-感知-接收（T-S-R）工作模式的同时收发认知抗干扰（SCAJ）技术,通过在感知/接收周期内动态分配感知、接收时隙而实现实时抗干扰。针对所提同时收发抗干扰策略,研究了基于能量检测的干扰感知性能,推导出衰落信道下干扰检测概率的闭式表达,并分析了同时收发认知抗干扰系统容量。仿真结果表明,提出的同时收发认知抗干扰技术提升了网电空间数据链的干扰感知能力,且在自干扰较低时能够提高网电空间数据链系统容量。     

A survey of radar ECM and ECCM

Radar electronic countermeasure (ECM) and electronic counter-countermeasures (ECCM) form the principal conflicting pair in modern electronic warfare. The technical history and state of art of both the radar ECM and ECCM are surveyed and their development trends are predicted. The classification of ECCM techniques, compatibility of various ECCM devices in a radar system and effectiveness evaluation of radar ECM and ECCM systems are also discussed     

Vector subspace detection in compound-Gaussian clutter. Part I: survey and new results

Deals with the problem of detecting subspace random signals against correlated non-Gaussian clutter exploiting different degrees of knowledge on target and clutter statistical characteristics. The clutter process is modeled by the compound-Gaussian distribution. In the first part of the paper, the optimum Neyman-Pearson (NP) detector, the generalized likelihood ratio test (GLRT), and a constant false-alarm rate (CFAR) detector are sequentially derived both for the Gaussian and the compound-Gaussian scenarios. Different interpretations of the various detectors are provided to highlight the relationships and the differences among them. In particular, we show how the GLRT detector may be recast into an estimator-correlator form and into another form, namely a generalized whitening-matched filter (GWMF), which is the GLRT detector against Gaussian disturbance, compared with a data-dependent threshold. In the second part of this paper, the proposed detectors are tested against both simulated data and measured high resolution sea clutter data to investigate the dependence of their performance on the various clutter and signal parameters.     

Adaptive polarimetric target detection with coherent radar. II.Detection against non-Gaussian background

For pt. I see ibid., vol. 37, no. 4, pp. 1194-1206 (2001).This paper presents the derivation of a polarimetric coherent adaptive scheme to detect a radar target against a non-Gaussian background. This completes the results presented in Part I for the Gaussian background. A Texture Free-Generalized Likelihood Ratio Test (TF-GLRT) detector is derived that exploits the polarimetric characteristics of the received radar echoes to improve the detection performance. The proposed polarimetric detector is shown to have Constant False Alarm Rate (CFAR) when operating against compound-Gaussian clutter with unknown parameters. Its performance is fully characterized by both theoretical analysis and simulation. Moreover, the application to recorded radar data demonstrates the performance improvement achievable in practice     

Adaptive polarimetric target detection with coherent radar. I.Detection against Gaussian background

The derivation of a completely adaptive polarimetric coherent scheme to detect a radar target against a Gaussian background is presented. A previously proposed Generalized Likelihood Ratio Test (GLRT) polarimetric detector is extended to the case of a general number of channels; this exploits the polarimetric characteristics of the received radar echoes to improve the detection performance. Together with the fully adaptive scheme, a model-based detector is derived that has a lower estimation loss. A complete theoretical expression is derived for the detection performance of both proposed polarimetric detectors. They are shown to have Constant False Alarm Rate (CFAR) when operating against Gaussian clutter, but to be sensitive to deviations from the Gaussian statistic. The application to recorded radar data demonstrates the performance improvement achievable in practice     

两种自适应方向图峰值副瓣控制方法比较

自适应阵列（或称自适应波束形成）目前已广泛应用到雷达、声纳和通信领域中用来抑制各种干扰（有意的干扰，杂波干扰和多用户干扰等）。在雷达应用中，为了减轻脉冲欺骗式干扰或旁瓣目标并利用单脉冲雷达来准确测量目标波达方向．要求自适应方向图具有低副瓣和稳定的主瓣形状。在实际应用中，各种失配误差将降低自适应阵列的性能．这些误差包括由于目标的波达方向不精确引起的信号指向误差，由通道失配和位置扰动引起的阵列校准误差和由小样本教引起的协方差矩阵估计误差。在此情况下，自适应波束形成的性能大大下降（干扰抑制性能变差。主瓣失真和高的副瓣）。已提出了一种基于二次约束的集成峰值副瓣控制（integrated peak sidelobe control，简称IPSC）方法。该方法可以精确地控制峰值副瓣电平并产生具有稳定的主瓣形状的自适应方向图。研究IPSC中目标信号的影响和信号消除方案以进一步提高IPSC的性能。并将IPSC方法和最新提出的基于二阶锥规划（second-order cone programming，简称SOCP）的分布式峰值副瓣控制（distfibuted peak sidelobe control，简称为DPSC）新方法在性能上进行了比较。仿真结果表明。在干扰抑制性能和方向图控制质量方面IPSC比DPSC性能优越。此外IPSC比DPSC计算高效。     

基于STFRFT的LFM引信抗欺骗干扰方法

针对线性调频脉冲压缩引信易受转发式假目标欺骗干扰问题,提出了基于短时分数阶傅立叶变换(STFRFT)的抗欺骗干扰方法。首先,通过分数阶傅立叶变换将回波信号与欺骗干扰各分量信号进行分离;再利用相同调频率的LFM信号经短时分数阶傅立叶变换后最大幅值与窗函数宽度成线性关系,而不同调频率的最大幅值不随窗函数宽度变化的特点,有效分辨假目标欺骗干扰,正确检测目标回波信号;最后,通过仿真证明了方法的正确性,并验证所提方法具有良好的抗欺骗干扰效果。     

基于PSO-ELM的卫星导航欺骗式干扰检测CSCD

近年来,卫星导航系统在军事监测、精细农业、交通监控、资源勘探、灾害评估等领域得到了广泛应用,但由于卫星导航信号结构公开且到达地面时强度微弱,卫星导航系统极易受到各种各样的干扰,其中欺骗式干扰因具有较强的隐蔽性,对卫星导航系统构成巨大的安全威胁。传统的欺骗式干扰检测方法大多采用单一参数进行检测,具有一定局限性。考虑到欺骗干扰源在欺骗过程中会引起一系列参数变化,构造了一个多参数输入的卫星导航欺骗式干扰检测模型,即将多个特征参数作为极限学习机(ELM)的输入,并通过训练和学习将真实信号与欺骗信号区分开,从而实现欺骗式干扰检测。同时,利用粒子群优化(PSO)算法优化ELM中的输入权值矩阵和隐层偏置,改善由于网络参数随机生成导致分类精度低的问题。仿真实验证明了该方法在卫星导航欺骗干扰检测方面的可行性和有效性。     

Neural network-based fault diagnosis for spacecraft with single-gimbal control moment gyros

This paper proposes a neural network-based fault diagnosis scheme to address the problem of fault isolation and estimation for the Single-Gimbal Control Moment Gyroscopes(SGCMGs) of spacecraft in a periodic orbit. To this end, a disturbance observer based on neural network is developed for active anti-disturbance, so as to improve the accuracy of fault diagnosis.The periodic disturbance on orbit can be decoupled with fault by resorting to the fitting and memory ability of neural network. Subsequ...     

Spatial adaptive subspace detection in OTH radar

The work presented here addresses the problem of target detection against spatially structured interference composed of jamming plus noise, where for practical reasons, the received target wavefront may also deviate from the traditional plane wave model. This detection problem arises in over-the-horizon (OTH) radar systems where spatially distributed targets often compete for detection against directional interference that is spread over the entire range-Doppler search space. Conventional detection processing schemes are compared with a recently proposed adaptive subspace detector (ASD) that takes both the spatial structure of the interference and the possibility of target wavefront distortions into account. Experimental array data recorded by the Jindalee sky-wave and Iluka surface-wave OTH radar systems, located in central and northern Australia respectively, is used to evaluate detection performance.