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.     

Enhanced motion and sizing of bank in moving-bank MMAE

The focus of this research is to provide methods for generating precise parameter estimates in the face of potentially significant parameter variations such as system component failures. The standard multiple model adaptive estimation (MMAE) algorithm uses a bank of Kalman filters, each based on a different model of the system. Parameter discretization within the MMAE refers to selection of the parameter values assumed by the elemental Kalman filters, and dynamically redeclaring such discretization yields a moving-bank MMAE. A new online parameter discretization method is developed based on the probabilities associated with the generalized chi-squared random variables formed by residual information from the elemental Kalman filters within the MMAE. This new algorithm is validated through computer simulation of an aircraft navigation system subjected to interference/jamming while attempting a successful precision landing of the aircraft.     

欺骗环境下GNSS信号估计与定位修正技术

欺骗信号以其极强的隐蔽性使卫星导航接收机难以察觉并迅速定位到错误位置,严重影响了卫星导航的安全性。现有抗欺骗技术需要其他导航系统辅助来修正受欺骗影响的定位解算,针对该问题,本文提出了一种GNSS欺骗信号参数估计与辨识方法,能够在欺骗干扰环境下估计并辨识出真实信号所对应的伪距,进而解算出接收机真实位置。该方法通过研究欺骗干扰下接收机相关值模型,在信号跟踪阶段建立真实与欺骗双信号状态模型与基于九路相关器输出的观测模型,利用扩展卡尔曼滤波（EKF）估计真实信号与欺骗信号的伪码延时与信号相关幅值,进而获得真实与欺骗伪距,在定位解算阶段利用改进观测量残差检测方法辨识出真实与欺骗伪距,最终使用真实伪距定位获得真实位置。仿真结果表明对相对码延时介于0.3~0.9 chip之间且欺骗/真实信号幅度比介于1~5之间的隐蔽欺骗攻击,所提方法的码延时估计误差约0.1 chip,可有效估计真实信号与欺骗信号参数,辨识出真实伪距,并使被欺骗的定位结果重新回到真实位置结果,改善GNSS接收机抗欺骗能力,提高卫星导航安全性。     

Multipath-adaptive GPS/INS receiver

Multipath interference is one of the contributing sources of errors in precise global positioning system (GPS) position determination. This paper identifies key parameters of a multipath signal, focusing on estimating them accurately in order to mitigate multipath effects. Multiple model adaptive estimation (MMAE) techniques are applied to an inertial navigation system (INS)-coupled GPS receiver, based on a federated (distributed) Kalman filter design, to estimate the desired multipath parameters. The system configuration is one in which a GPS receiver and an INS are integrated together at the level of the in-phase and quadrature phase (I and Q) signals, rather than at the level of pseudo-range signals or navigation solutions. The system model of the MMAE is presented and the elemental Kalman filter design is examined. Different parameter search spaces are examined for accurate multipath parameter identification. The resulting GPS/INS receiver designs are validated through computer simulation of a user receiving signals from GPS satellites with multipath signal interference present The designed adaptive receiver provides pseudo-range estimates that are corrected for the effects of multipath interference, resulting in an integrated system that performs well with or without multipath interference present.     

基于Starlink机会信号/INS的组合导航方法

针对全球卫星导航系统(GNSS)因频点单一、落地功率低、易受电磁干扰以及存在覆盖较差区域等潜在的被拒止或被干扰导致的导航系统性能降低甚至失效的问题,提出了一种基于星链(Starlink)机会信号融合惯性导航系统(INS)的飞行器动态组合导航方法。首先分析了星链信号体制,建立了基于星链星座卫星下行机会信号的瞬时多普勒定位观测模型,设计了一种基于频率细分的快速最大似然多普勒频率估计方法,然后建立了基于扩展卡尔曼滤波(EKF)的Starlink机会信号/INS的组合导航模型,并对该导航方法进行了实验及分析。结果表明,该方法可为飞行器提供长航时、连续、高精度的导航。动态飞行情况下,该方法可实现平均优于25 m的三维定位精度和平均优于0.1 m/s的速度估计精度,比相同观测时间下的惯导精度提高了1～2个数量级,显著提高了飞行器的导航精度,可为战略导航提供方法和技术支撑。     

一种基于多基线载波相位差测量的欺骗干扰检测方法

由于卫星导航信号到达地面的信号功率较低,且民用部分信息公开,极易受到欺骗干扰信号的影响,从而导致接收机解算出错误的位置、速度或时间.针对传统的欺骗干扰检测与抑制方法不能对欺骗干扰进行测向的问题,提出了一种基于阵列多天线接收信号的载波相位差进行欺骗信号检测与抑制的方法.该方法能够在缺少先验知识的条件下,借鉴相关干涉仪测向...     

基于载噪比同步变化的北斗欺骗检测方法

欺骗干扰已经成为北斗卫星导航系统安全性的一个严重威胁。针对北斗系统面临的欺骗干扰问题,建立二元假设检验模型。由于施加单一天线发射的欺骗干扰后,当前观测频点下各高俯仰角可见星的载噪比值会产生相同的变化趋势,所以基于此变化规律提出了一种利用K-means聚类算法进行分析的北斗卫星信号欺骗干扰检测方法,并给出了施加欺骗载噪比变化域的定义。最后通过在外场搭建实验环境,对实采数据进行了实验验证。实验结果表明,本方法对于欺骗功率优势≥6 dBm的大功率优势欺骗信号的检测概率可以达到95%以上,为提高接收机抗干扰能力提供了有益参考。     

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。     

Ranging airport pseudolite for local area augmentation

This paper discusses the integration of an airport pseudolite (APL) into a local area augmented differential GPS based precision approach system. A prototype architecture is described that is being used to develop requirements for the local area augmentation system. Key features of this prototype system are presented along with its current performance. Key features discussed include the use of a multipath limiting antenna, APL signal structure factors, a unique APL automatic gain control, and GPS blanking technique to maximize APL tracking performance, while minimizing the electromagnetic interference to nominal DGPS performance     

利用旋转双天线载波相位双差的欺骗干扰检测技术

有效的欺骗干扰检测是防止卫星导航接收机被欺骗干扰攻击的前提。提出了一种基于旋转双天线载波相位双差的卫星导航接收机欺骗干扰检测技术,在对接收机双天线匀速旋转时输出载波相位测量值进行载波相位双差处理后,利用广义似然比检验实现了对单一发射天线输出欺骗干扰信号的检测。进一步分析了旋转半径和数据长度对检测性能的影响,并与旋转单天线和天线阵载波相位双差欺骗干扰检测方法的性能进行了对比。最后,通过蒙特卡罗方法进行了仿真验证,结果表明了该检测方法和检测性能分析的正确性。     

基于INS/GNSS紧耦合组合的逐步诱导式欺骗检测算法研究

传统惯性辅助GNSS欺骗信号检测方法对小于纯惯导误差漂移的逐步拉偏不敏感。针对这一问题,提出了一种基于INS/GNSS紧耦合组合的逐步诱导式欺骗信号检测方法。基于短时间内纯惯性导航结果和短时间惯导系统位置误差传播模型,利用惯导提供的位置和速度对伪距和伪距率时间序列进行预测估算,并结合伪距、伪距率实际测量结果,分别构造位置/伪距和速度/伪距率时间序列模型做参数拟合。基于真实信号得到的模型参数都是由惯导系统误差造成的,具有一致性;而基于逐步诱导式欺骗信号得到的模型参数还与欺骗策略的设定、载体飞行轨迹的观测以及干扰源的位置有关,具有不一致性。通过对比模型参数可判别欺骗信号的存在,对于真实信号,采用紧耦合组合导航修正INS输出;对于欺骗信号,继续惯性导航并采取相应措施。最后,根据逐步诱导式欺骗原理进行实验仿真,验证了算法的可行性和有效性。     

Performance enhancement of a multiple model adaptive estimator

We describe performance improvement techniques for a multiple model adaptive estimator (MMAE) used to detect and identify control surface and sensor failures on an unmanned flight vehicle. Initially failure identification was accomplished within 4 s of onset, but by removing the “β dominance” effects, bounding the hypothesis conditional probabilities, retuning the Kalman filters, increasing the penalty for measurement residuals, decreasing the probability smoothing, and increasing residual propagation, the identification time was reduced to 2 s     

SINS/BDS紧组合系统中自适应 两阶段扩展卡尔曼滤波

在实际应用中，以伪距/伪距率为观测量的SINS/BDS紧组合导航系统，存在量测噪声的统计特性与实际不相符的情况，传统扩展卡尔曼滤波（EKF）方法无法有效解决这一问题，从而引起滤波误差增大。提出了一种SINS/BDS紧组合导航系统的GDOP估算及在线估计量测噪声的自适应两阶段EKF（ATEKF）方法，该方法使用经过紧组合修正后的SINS输出的位置，并结合星历数据中提供的卫星位置求解GDOP。在此基础上，利用GDOP值以及新息，实现了紧组合导航系统的量测噪声方差阵（Rk）的在线实时估计，从而达到自适应滤波的效果，改善导航精度。     

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).     

基于MIMU的适应多步态的步行导航算法

针对目前国内外步态导航算法中引入的零速检测大都不能很好的对多种步态的行走进行辨识的问题,提出了基于低成本MIMU（微惯性测量单元）、且能兼容多种步态的步行导航算法。算法通过采集安置在行人脚部MIMU输出的测量信息,用捷联惯性积分算法进行导航解算。其间,提出一种新的零速检测方法对行走时变化的步速和步型进行准确辨识,进而找到脚步的零速时刻点,并通过设计的扩展卡尔曼滤波（EKF）对导航解算结果进行零速修正（ZUPT）,实现系统的反馈。最后进行两组实验对算法验证。结果表明,该步态导航算法能对行走时的多步态问题有很好的兼容性,零速修正时刻辨识准确度高,两组实验的导航解算误差均达到0.6%以内,进一步提高了步态导航算法的精度和实用性。     

无人机下滑着陆DGPS/INS导航及引导系统的仿真与试验研究

介绍了一种采用输出校正方式DGPS/INS组合导航系统引导无人机下滑着陆的方案。给出了该方案的数学模型,对组合导航系统进行了数字仿真,并在数字仿真的基础上进行了动态跑车试验,验证了所设计的输出校正方式DGPS/INS组合导航系统能够满足引导无人机自动下滑着陆的精度要求。     

Carrier phase navigation architecture for shipboard relative GPS

Carrier phase differential GPS (DGPS) navigation architectures and algorithms for automatic shipboard landing of aircraft are described. Processing methodologies are defined to provide high integrity carrier phase cycle estimation and positioning by optimally exploiting the complementary benefits of measurement filtering and satellite geometric redundancy for the terminal navigation problem. Navigation performance sensitivity to the standard deviations of raw carrier and code phase measurement errors, measurement error correlation times, and the filtering duration is quantified. Necessary conditions to ensure acceptable terminal navigation availability are specifically defined.     

Multiple model adaptive estimation with filter spawning

Multiple model adaptive estimation (MMAE) with filter spawning is used to detect and estimate partial actuator failures on the VISTA F-16. The truth model is a full six-degree-of-freedom simulation provided by Calspan and General Dynamics. The design models are chosen as 13-state linearized models, including first order actuator models. Actuator failures are incorporated into the truth model and design model assuming a "failure to free stream." Filter spawning is used to include additional filters with partial actuator failure hypotheses into the MMAE bank. The spawned filters are based on varying degrees of partial failures (in terms of effectiveness) associated with the complete-actuaton-failure hypothesis with the highest conditional probability of correctness at the current time. Thus, a blended estimate of the failure effectiveness is found using the filters' estimates based upon a no-failure hypothesis, a complete actuator failure hypothesis, and the spawned filters' partial-failure hypotheses. This yields substantial precision in effectiveness estimation, compared with what is possible without spawning additional filters, making partial failure adaptation a viable methodology.     

跟飞编队卫星相对导航自适应EKF算法研究

针对跟踪星对目标星跟飞编队的相对导航问题,提出了基于自适应扩展卡尔曼滤波（EKF）的相对导航算法。以线性离散化的椭圆参考轨道相对动力学模型为导航状态方程．设计了虚拟测量量及相应的测量矩阵,避免了求解雅可比矩阵的复杂计算。为了适应构型尺寸变化引起的模型误差变化,提出了模型误差在线估计算法。仿真显示,算法具有较快的收敛速度和较高的估计精度。该研究成果可作为卫星编队应用的有益参考。     

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.