基于预估-反馈联合处理的射频噪声干扰抑制算法

针对强射频（RF）噪声干扰下脉压雷达目标检测概率较低的问题,提出了一种基于预估-反馈联合处理的射频噪声干扰抑制算法。首先,对回波信号进行盲源分离预处理,并利用分数阶傅里叶变换（FRFT）的特性对目标回波信号进行参数估计以及窄带滤波处理,滤除大部分干扰和噪声的能量;然后,在数据层运用M/N逻辑法进行点迹处理,并结合径向速度方向判决,实现对目标航迹的预估检测;最后,利用数据层对航迹状态的反馈实时修正滤波器参数,从而在信号层更好地滤除干扰能量,并对中断航迹进行剔除,完成射频噪声干扰的抑制。仿真结果表明：与现有射频噪声干扰抑制技术相比,所提算法具有更优的干扰抑制效果。     

STAP for GPS receiver synchronization

A space-time adaptive processing (STAP) algorithm for delay tracking and acquisition of the GPS signature sequence with interference rejection capability is developed. The interference can consist of both broadband and narrowband jammers, and is mitigated in two steps. The narrowband jammers are modelled as vector autoregressive (VAR) processes and rejected by temporal whitening. The spatial ing is implicitly achieved by estimating a sample covariance matrix and feeding its inverse into the extended Kalman filter (EKF). The EKF estimates of the code delay and the fading channel are used for a t-test for acquisition detection. Computer simulations demonstrate robust performance of the algorithm in severe jamming, and also show that the algorithm outperforms the conventional delay-locked loop (DLL).     

A Logarithmic Frequency Allocation Algorithm for Wideband Discrete Frequency Pulse Trains

It is shown that signal waveforms utilizing discrete frequency modulation (DFM) which are generated using a narrowband or frequency shift algorithm have ambiguity sidelobe distortion which is caused by the approximation of time compression by frequency shift. A logarithmic frequency allocation algorithm is presented which couches the signal design problem in terms of band and step ratios, rather than in terms of bandwidth and frequency steps, and is consistent with the wideband formulation of the ambiguity function. The algorithm makes use of the same basic code generating sequence used for narrowband frequency allocation, but the resulting signal will have invariant ambiguity sidelobe positions for any receiver realization in the delay-time compression plane.     

基于拖曳式干扰机的ISAR微动散射波干扰方法

通过对微多普勒效应的研究,提出了一种新的逆合成孔径雷达（ISAR）散射波干扰方法。将拖曳式干扰机和ISAR接收机分别等效为双基ISAR的发射站和接收站,干扰机对截获的ISAR信号进行微动信息调制并转发至目标,由其散射至ISAR接收机产生散射波干扰效果。干扰信号经ISAR接收机处理后可在真实目标回波成像结果附近产生假目标,且在方位向形成干扰条带。实验结果表明：通过控制干扰机转发参数及微动调制参数可分别实现不同的压制干扰效果。由于拖曳式干扰机与目标距离较近,干扰信号可获得较大功率,且与真实目标回波相参,可获得ISAR二维脉冲压缩处理增益,与传统射频噪声压制干扰方法相比成本较小。     

Volume Properties for the Wideband Ambiguity Function

It is shown that the volume under the wideband ambiguity function is close to the square of the signal energy. The ambiguity volume is asymptotically conserved as the signal approaches the narrowband case. The narrowband ambiguity volume is a lower bound for the volume of the wideband ambiguity function.     

Hybrid discriminative/class-specific classifiers for narrowband signals

The class-specific (CS) method of signal classification operates by computing low-dimensional feature sets defined for each signal class of interest. By computing separate feature sets tailored to each class, i.e., CS features, the CS method avoids estimating probability distributions in a high-dimension feature space common to all classes. Building a CS classifier amounts to designing feature extraction modules for each class of interest. In this paper we present the design of three CS modules used to form a CS classifier for narrowband signals of finite duration. A general module for narrowband signals based on a narrowband tracker is described. The only assumptions this module makes regarding the time evolution of the signal spectrum are: (1) one or more narrowband lines are present, and (2) the lines wandered either not at all, e.g., CW signal, or with a purpose, e.g., swept FM signal. The other two modules are suited for specific classes of waveforms and assume some a priori knowledge of the signal is available from training data. For in situ training, the tracker-based module can be used to detect as yet unobserved waveforms and classify them into general categories, for example short CW, long CW, fast FM, slow FM, etc. Waveform-specific class-models can then be designed using these waveforms for training. Classification results are presented comparing the performance of a probabilistic conventional classifier with that of a CS classifier built from general modules and a CS classifier built from waveform-specific modules. Results are also presented for hybrid discriminative/generative versions of the classifiers to illustrate the performance gains attainable in using a hybrid over a generative classifier alone.     

一种组合型的探干一体化信号设计分析

针对雷达信号资源利用率有待提升、低截获性能不足的问题,提出 1种复合调制的创新型探干一体化信号波形。线性调频信号本身具有良好的低截获性能,伪随机码序列分量具有较好的干扰性,同时又能一定程度上扩展信号带宽,两者的复合调制信号具有良好的探测和干扰性能。对基于 LFM的探干一体化信号波形进行了调制原理分析,并分别从时域、频域、功率谱、模糊函数、自相关特性等角度分析其探测、干扰特性。仿真实验证明,相较于单一调制的线性调频信号,一体化信号具有更宽的频带、更优良的干扰特性和探测性能,同时,有更高效的雷达资源利用率。     

灵巧噪声干扰本质含义探讨

文章对灵巧噪声干扰概念的表述提出了质疑,在多项质疑中选取了SLB技术进行简要分析,并指出,SLC等抗干扰技术的作用与是否实施灵巧噪声干扰没有直接关系。进一步,基于匹配滤波器理论对灵工j噪声干扰的本质含义进行了分析,指出：灵巧噪声干扰的本质含义是使干扰由多个分量组成,并且使干扰中的每一个分量的频谱都与雷达发射信号的频谱相...     

Susceptibility of DS/FH,M, Binary DPSK to Partial and Full Band Barrage Jamming

Spread spectrum signaling schemes have been proposed to counter unfriendly, electrical jamming threats. In order to establish their effectiveness, such schemes must be analyzed. This work takes a step in this direction by developing the susceptibility equation, or equivalently, the probability of error, of a direct sequence/frequency hopped (DS/FH), binary differential phase-shift keying (DPSK) system when subjected to a barrage jamming signal. Specific system models are established for the receiving system as well as for the jamming signal and the spread spectrum techniques. Both partial and full band jamming strategies are considered. Graphical results are presented with the conclusions summarizing the spread spectrum effectiveness and the deficiencies of the FH processing gain definition.     

一种对GPS/INS组合导航的曳引式拉偏干扰

为解决GPS/INS组合导航对抗难题,提出一种针对GPS/INS组合导航的曳引式拉偏干扰方法。通过干扰设备产生欺骗干扰信号,使GPS/INS组合中的GPS接收机输出与其实际位置逐渐偏离的导航定位数据,当偏离误差无法被组合导航纠正时发生曳引式拉偏干扰。文中给出干扰方法的定义、信号形式、简化形式,通过半实物仿真实验证明其有效性并对其干扰效果进行了分析。     

Correspondence - Optimum Radar Signal for Detection in Clutter

It is shown that in order to maximize the detectability of a radar target in clutter whose Doppler is unknown and is uniformly distributed over the Doppler bandwidth a simple CW or narrowband signal is optimal. The optimality criterion is the average deflection coefficient, with the averaging being over target Doppler frequency. Most remarkably the result does not depend on the clutter spectrum but holds for any distribution of clutter energy with frequency.     

Error Probability for NCFSK with Linear FM Jamming

An expression is derived for the probability of error for a conventional binary, noncoherent, frequency-shift-key (NCFSK) communications system under the influence of bandpass Gaussian noise and a linear frequency-modulation jamming waveform. The resulting integral is expressed in terms of the well-known Q function, which depends upon average signal, noise, and jamming powers. The analytical procedures used can be applied to the analysis of the effects of other types of jamming.     

The Effect of Hard Limiting in the Presence of Large Out-of-Band Interfering Signals

The effect of hard limiting on the phase of a test signal was investigated when large out-of-band interfering signals are present at the input to the limiter. First a single and then two discrete interfering signals were considered. The interfering signals and the test signal are restricted to narrow but separated bands. The test signal is recovered after limiting by narrowband filtering. The analysis of the single interfering signal is essentially the same as that performed by Cahn.1 In this correspondence experimental evidence is presented to verify the analysis and, in addition, the case of two interfering signals is considered.     

Detection of long-duration narrowband processes

Detecting long, weak signals that are narrowband but of unknown frequency structure is an important signal processing challenge, with many applications in remote sensing and process monitoring. An ad hoc scheme is developed. Its stages include the discrete Fourier transform (DFT), a multiresolution decomposition in the frequency domain, and a generalized likelihood ratio test (GLRT). The computational load is light, and the performance is remarkably good. This is so not just in the original narrowband situation, but also, due to an inherent adaptivity to the data, in the detection of signals that are relatively broadband in nature. Generalizations are given to constant false alarm rate (CFAR) operation in both prewhitened and unwhitened cases, and to the detection of multiband signals. As regards the last, it is discovered that there is little loss from overestimating the number of bands     

基于四阶累积量和小波降噪的干扰抑制算法

针对盲信号分离算法在低信噪比下分离效果较差的情况,提出了一种基于四阶累积量和小波降噪的含噪盲分离算法,并将该算法用于卫星通信干扰抑制。首先,利用基于四阶累积量的盲分离算法进行信扰盲分离;然后对分离出的已被噪声污染的通信信号进行小波降噪处理。最后,对提出的算法在单音干扰下进行了性能仿真。仿真结果表明,该算法不仅使抗噪性能提高了3dB左右,而且在低信噪比下对强单音干扰具有较好的抑制效果。     

EMD的频带滤波筛分方法

Hilbert—Huang（HHT）变换方法由经验模态分解（EMD）及Hilbert变换两部分组成,能在时频域上正确地描述非平稳非线性信号的局部特征。但由于模态混淆,当信号组合分量的频率太接近时,HHT常不能正确分解窄带信号。针对这一情况,提出了EMD筛分过程的一种新的改进方法——频带滤波HHT方法,并运用此方法成功分解了双自由度线性体系反应的窄带信号。     

分布式干扰对TH-PPM-UWB通信干扰的仿真分析

从通信干扰角度,本文首先讨论了分布式干扰的功率优势,重点分析了分布式干扰(音调干扰信号)对TH-PPM-UWB通信系统的干扰效果,并运用蒙特卡洛实验方法对干扰效果进行了仿真,最后综合理论和仿真给出了部分有益的结论。     

基于Doppler估计的弹载接收机抗欺骗干扰研究

GNSS接收机在军用方面尤其是高精度制导武器中的应用日益增强.针对卫星信号易受敌方欺骗信号干扰的问题,设计一种基于Doppler频率估计的弹载接收机抗欺骗干扰的方法.首先分析了欺骗干扰和真实信号的Doppler变化特点;然后在捕获阶段利用残留信号检测存在欺骗干扰的卫星编号;最后根据弹载的高动态特性,在跟踪阶段采取扩展 Kalman 滤波器(EKF)进行载波Doppler频率估计,并根据Doppler变化的相似性提取出欺骗信号.通过仿真实验验证,该方法可以有效排除欺骗信号的干扰.     

对GPS／INS制导巡航导弹GPS干扰方法的探讨

目前GPS/INS制导已成为精确制导武器的核心。本文根据GPS信号特点及GPS/INS制导机理,通过对压制干扰和欺骗干扰技术及其对GPS接收机影响的分析,着重探讨对GPS/INS制导巡航导弹GPS干扰的方法。若要提高对GPS/INS制导巡航导弹实施远距离干扰的效果,而又使干扰机功率不是很大,则需建立多层次、分布式、立体式、小功率GPS干扰体系。     

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