Research on adaptive notch filter cascading neural network anti-jamming algorithm

Satellite navigation suffers from performance degradation in the presence of narrowband interference. We present a Global Positioning System(GPS) receiver anti-jamming algorithm based on the neural network. The method combines the adaptive notch filter with the Back Propagation(BP) neural network. We first use the two order lattice infinite impulse response adaptive notch filter to eliminate-out-of-band jamming, then use the BP neural network predictor to estimate and cancel jamming. We analyze three aspects of algorithm performance which include acquired satellite numbers,signal-to-noise improvements and iteration numbers. Simulation results show that the method can effectively suppress narrowband interference and has a better anti-jamming capacity and a faster convergence speed.     

面向无人机的逐点偏移式卫星导航欺骗干扰方法

针对无人机在失控肇事、干扰航管、窥视窃密、恐怖袭击等方面的危害,本文提出一种基于逐点拉偏式卫星导航欺骗方法,通过重构错误的导航坐标系诱骗目标无人机飞离敏感区域保护地面安全。该方法将整个无人机欺骗过程看作是单步位置欺骗拉偏的时间迭代过程,首先根据无人机的运动学模型以及外部量测信息估算出无人机的真实位置点以及真实控制输入量;然后考虑无人机飞行控制器对欺骗效果的影响,在真实控制输入量中抵消掉预先设置的欺骗控制力矩效果,设计构造虚假卫星信号使得GNSS/INS组合导航模式下的滤波估计无人机位置点仍靠近原始期望目标点,但发生了偏差;最后这种偏差产生的无人机轨迹跟踪控制输入量会导致无人机真实状态点往欺骗目标点偏移,实现单步卫星导航欺骗效果。单步欺骗过程在时间上的迭代运用,可实现无人机位置的逐点偏移式欺骗。仿真结果显示利用逐点偏移式卫星导航欺骗方法能使得目标无人机慢慢偏离原始轨迹而跟踪欺骗轨迹,且组合导航滤波器估计轨迹仍跟踪原始参考轨迹,达到了卫星导航欺骗的目的。本文提出的基于逐点拉偏式卫星导航欺骗干扰技术可用于保障重点区域/人员的低空安全防护。     

北斗卫星导航系统的应用及其抗干扰技术

介绍了北斗卫星导航系统组成、信号特点及其应用领域,然后指出北斗卫星导航信号的宜被干扰性,概述了目前主要采用的干扰与抗干扰技术,最后提出应从国家安全层面认识北斗卫星导航的抗干扰问题。     

GNSS信号体制抗干扰性能分析

以干扰等效载噪比和码跟踪误差为干扰效果评估指标,对当前GPS和Galileo卫星导航信号体制受单频、带限高斯噪声和匹配谱干扰的影响程度分别进行了理论推导和仿真分析,得到信号调制方式和接收机参数设置与增强抗干扰性能的内在联系。在此基础上,将北斗卫星导航系统(BDS)信号体制与GPS和Galileo进行比较,得出BDS的B1-C可优化为CBOC(6,1,1/11)的调制组合方式、B2可设计为导频通道伪随机调制序列相同的TD-AltBOC(15,10)调制、B1-A和B3-A可分别采用TDDM-BOC_c(15,2.5)和BOC_c(15,2.5)调制的信号抗干扰性能增强建议。     

Jamming Monitoring Technology of the Space Situational Awareness Facilities: A Comprehensive Survey

Complicated electromagnetic environments of the space situational awareness facilities (i.e., satellite navigation systems, radar) would significantly impact normal operations. Effective monitoring and the corresponding diagnosis of the jamming signals are essential to normal operations and the innovations in anti-jamming equipment. This paper demonstrates a comprehensive survey on jamming monitoring algorithms and applications. The methods in dealing with jamming signals are summarized primarily. Subsequently, the jamming detection, identification, and direction finding techniques are addressed separately. Based on the established studies, we also provide some potential trends of the demonstrated jamming monitoring issues.     

HLA/RTI卫星导航对抗仿真技术研究

卫星导航系统是一种高精度的天基导航系统,它逐渐代替了地面区域的导航系统,这一变革将从体制上改变航空业、航海业的现状,也给人们的日常生活和生产带来了前所未有的变化。为了更好地掌握卫星导航技术并且有效试验和演示导航系统下的干扰和抗干扰、欺骗和防欺骗的新技术和新思想,借助分布式高层体系结构HLA/RTI建立卫星导航对抗的仿真系统,并在此仿真系统下展开对卫星导航系统相关技术的研究。在仿真系统中采用适当的时间推进使得各仿真成员时间一致,采取合理的数据分发机制以减少数据的冗余和网络资源的浪费.     

对GPS/INS超紧耦合导航对抗的干扰源配置分析

GPS/INS组合技术广泛应用于精确制导武器导航中,随着GPS/INS组合导航超紧耦合方式的逐渐成熟,整个导航系统的抗干扰能力显著提升。为了对采用GPS/INS超紧耦合精确制导武器有效实施导航对抗,以GPS接收机不同环节的性能下降指标将干扰形成的威力区用受扰区、半失效区和失效区来进行划分,结合接收机工作过程和GPS/INS超紧耦合对接收机跟踪环结构设计的影响,推导分析了在匹配谱干扰下P(Y)码和M码信号捕获、跟踪和解调性能指标降至划分临界值时接收机射频前端所需的干扰功率。考虑干扰来向与接收天线增益的关系,仿真得到干扰源在不同高度下各威力区发射功率随有效距离的变化关系。在此基础上,对GPS/INS超紧耦合精确制导武器的导航对抗连续压制作用距离进行仿真分析,进而完成对干扰源数量和部署位置的建模求解。分析和解算结果可为载荷和高度受限的升空干扰源在GPS/INS超紧耦合精确制导武器导航对抗中的实际运用提供借鉴和参考。     

GNSS软件接收机中相关捕获算法研究

为了适应全球卫星导航定位系统(GNSS)接收机的发展趋势,研究了一种GNSS软件接收机捕获多个星座卫星信号的相关捕获算法.该算法可以同时接收和处理GPS和Galileo两个系统L1频段内所有民用信号,通过仿真分析了影响算法性能的因素--本地复现序列数,并给出了利用Simulink和程序实现的算法来捕获两个系统民用信号的结果.结果表明,该算法可以很快地捕获到系统信号,具有灵活、方便、简单的特点,对软件接收机的设计有指导意义.     

A novel satellite-equipped receiver for autonomous monitoring of GNSS navigation signal quality

Global navigation satellite system (GNSS) comes with potential unavoidable application risks such as the sudden distortion or failure of navigation signals because its satellites are generally operated until failure. In order to solve the problems associated with these risks, receiver autonomous integrity monitoring (RAIM) and ground-based signal quality monitoring stations are widely used. Although these technologies can protect the user from the risks, they are expensive and have limited region coverage. Autonomous monitoring of satellite signal quality is an effective method to eliminate these shortcomings of the RAIM and ground-based signal quality monitoring stations; thus, a new navigation signal quality monitoring receiver which can be equipped on the satellite platform of GNSS is proposed in this paper. Because this satellite-equipped receiver is tightly coupled with navigation payload, the system architecture and its preliminary design procedure are first introduced. In theory, code-tracking loop is able to provide accurate time delay estimation of received signals. However, because of the nonlinear characteristics of the navigation payload, the traditional code-tracking loop introduces errors. To eliminate these errors, the dummy massive parallel correlators (DMPC) technique is proposed. This technique can reconstruct the cross correlation function of a navigation signal with a high code phase resolution. Combining the DMPC and direct radio frequency (RF) sampling technology, the satellite-equipped receiver can calibrate the differential code bias (DCB) accurately. In the meantime, the abnormities and failures of navigation signal can also be monitored. Finally, the accuracy of DCB calibration and the performance of fault monitoring have been verified by practical test data and numerical simulation data, respectively. The results show that the accuracy of DCB calibration is less than 0.1 ns and the novel satellite-equipped receiver can monitor the signal quality effectively.     

Anti-Jamming Algorithm Based on Spatial Blind Search for Global Navigation Satellite System Receiver

A novel subspace projection anti-jamming algorithm based on spatial blind search is proposed, which uses multiple single-constrained subspace projection parallel filters. If the direction of arrival (DOA) of a satellite signal is unknown, the traditional subspace projection anti-jamming algorithm cannot form the correct beam pointing. To overcome the problem of the traditional subspace projection algorithm, multiple single-constrained subspace projection parallel filters are used. Every single-constrained anti-jamming subspace projection algorithm obtains the optimal weight vector by searching the DOA of the satellite signal and uses the output of cross correlation as a decision criterion. Test results show that the algorithm can suppress the jamming effectively, and generate high gain toward the desired signal. The research provides a new idea for the engineering implementation of a multi-beam anti-jamming algorithm based on subspace projection.     

基于时域对消的抗噪声调频干扰算法仿真分析

为提高雷达的抗干扰能力,首先论述了噪声调频干扰的数学模型与主要参数,采用了基于时域对消的算法抗噪声调频干扰,给出了算法的数学推导过程．该算法通过对数变换,分别由信号的实部与虚部估计出干扰信号的瞬时幅度与瞬时频率,以此对干扰信号进行重构,最后再利用时域对消的方法抑制掉了干扰信号分量．最后进行了仿真验证,证明了该算法的有效性．     

Interrupted sampling repeater jamming suppression based on time-frequency analysis and band-pass filtering

Interrupted sampling repeater jamming is a new type of coherent jamming that generates a single or multiple false target groups,which cannot be effectively suppressed using conventional signal processing methods.To solve this problem,the received signals of several pulse repetition cycles are first accumulated in the time-frequency domain to enhance the time-frequency information on the signals.Then,the distribution of jamming signal is extracted accurately on the time-frequency surface based on the image processing algorithm,and the target echo is roughly reconstructed according to the time-frequency domain filtering method.Finally,based on the reconstructed time-domain signal,a band-pass filter is constructed to suppress the interference and noise.Simulation results indicate that compared with other methods,this scheme can effectively suppress various types of interrupted sampling repeater jamming in a low signal-to-noise ratio and multi-target environment with robustness and accuracy.     

基于检测器性能实时评估的欺骗检测融合算法

随着GPS欺骗生成技术的发展,欺骗信号可以在某一些属性上与真实信号保持一致,如到达角、多普勒频移等,此时单独使用某一种欺骗干扰检测方法,将无法有效地对欺骗信号进行检测,而如果采用直接将多种欺骗检测器结果相或的方法,则检测性能将会随着某一种检测器性能下降而下降.针对不同欺骗干扰场景下,检测器检测性能实时变化且先验信息缺失的情况,本文提出性能实时评估的欺骗检测融合算法.该方法通过建立性能误差评价准则,对融合后的检测性能与单个检测器性能进行实时比较,如果发现某一个检测器性能误差超过门限,则在融合过程中剔除该检测器,从而可以保证当一种检测器失效不会影响融合后的整体性能,该方法可以适用于任意数量,任意种类的欺骗检测方法融合,本文针对相位差和载波多普勒方差两种具体的检测方法,给出了工程实现方法.最后通过仿真结果表明,性能实时评估的欺骗检测融合算法与单独检测算法以及传统融合算法相比,具有更高的检测性能和更广的适应能力.     

GNSS欺骗干扰效能评估指标与方法研究综述

随着电磁环境的日益复杂,卫星导航的安全应用面临严峻挑战。作为导航对抗的核心技术之一,全球导航卫星系统(Global Navigation Satellite System, GNSS)欺骗干扰技术逐渐成为国内外研究的热点方向。基于此,以欺骗干扰技术为依托的GNSS欺骗干扰设备正从验证阶段迈入应用阶段,对其效能的有效评估并选取性能优的设备不仅能够增强现代化导航对抗实力,还将促进目标任务的成功。作为开展效能评估研究的理论基础,首先介绍GNSS欺骗干扰效能评估指标与评估方法的应用背景与研究进展,随后总结国内外学者围绕GNSS欺骗干扰效能评估指标与方法的研究现状,最后阐述当前针对该领域研究存在的不足和未来的发展趋势。     

水费计量远程抄表控制系统抗干扰技术

介绍了水费计量远程抄表控制系统的抗干扰问题.通过对控制系统计量结果以及周边环境的分析，找出主要干扰信号，并针对此干扰信号幅度大、脉宽大的特点，在软件上设计了具有特色的长延时软件滤波抗干扰措施，同时采用了相应的屏蔽、双绞线传输以及安装滤波电容等硬件抗干扰措施.通过以上软件及硬件两种抗干扰措施的实施，干扰信号被有效控制，系统的计量准确性得到了很大提高.实践表明，这些抗干扰措施简单易行、经济实用、提高了控制系统的可靠性.     

陆基增强/双星定位组合系统

提出了通过建立陆基增强系统来提高双星定位能力的技术方案，对该方案实施的可行性进行了理论分析，给出了陆基导航台和用户接收机的结构原理，分析设计了陆基导航台和双星的时间同步技术方案，对比研究了双星系统与陆基增强／双星系统的定位精度问题，得到了一些有参考价值的结论。增强后的双星系统用户端安装导航处理器，工作方式转为被动无源工作模式。分析表明，对双星系统增强后，提高了导航的可靠性，减小了定位几何系统GDOP，提高了定位精度。     

Wideband interference suppression based on space-time filter

Based upon the diagonal loading technique and the structure of the space-time adaptive processors,a novel anti-jamming method of satellite navigation is proposed. According to matrix inverse theorem,the range of the diagonal loading values for space-time adaptive wideband signal processing structure is deduced,and the optimum equation of diagonal loading beam forming algorithm of space-time structure is obtained. Then,by the analysis of two-dimensional oriented vector in direction of the perturbation interference,the wideband interference covariance matrix obtained in the weights training period is modified. Finally,the optimum weight of multi-linear constrained space-time adaptive beam-forming alogrithm is derived for anti-interference filter processing. The new method effectively widens the null steering beams when discrepancy happens. The computer simulation results prove the robustness of the proposed method.     

基于协作功率被动调整的 MIMO 系统安全容量算法

在由一个发射者、一个合法接收者、一个窃听者以及一个协作者组成的高斯MIMO系统窃听信道,发射者发射保密消息给合法接收者,同时协作者发射独立于保密消息信号的协作干扰信号,以此来干扰非法接收者对保密消息的接收。利用正定矩阵的性质获得了基于功率被动调整的协作干扰信号协方差矩阵的次优解,随后通过将高斯干扰信号看作高斯背景噪声,更新了发射者的发射协方差矩阵。仿真结果表明,该算法能够进一步提高MIMO系统的安全容量。     

双天线对消技术对宽带干扰的抑制性能

提出了一种应用在卫星导航系统中的干扰对消技术.通过理论推导,详细分析了干扰对消系统对宽带干扰抑制能力的极限值,揭示了带宽延时积与干扰对消比的内在关系,量化了幅度误差和相位误差对宽带干扰对消比的恶化程度.通过仿真和实验验证了理论分析的正确性.实验验证了双天线对消系统可使卫星导航接收机的抗干扰能力提高29 dB.     

低压电器干扰单片机的机理与对策

由于低压电器对单片机应用系统有严重的干扰,困扰了单片机的应用。通过智能式电能表的实践,探讨出低压电器干扰单片机的机理:感性元件的电磁干扰,触头的火花干扰以及单片机的电源遭受污染后导致单片机应用系统不能正常工作。提出相应的抗干扰对策:硬件抗干扰措施、软件抗干扰措施以及工艺方面抗干扰措施。通过智能式电能表的实践证明上述抗干扰的措施是行之有效的。