基于均值-方差联合检验的航迹欺骗干扰识别

以集中式融合结构雷达网为研究背景,从电子战飞机(ECAV)产生虚假航迹的原理出发,针对真/假航迹空间分布差异,提出了基于均值-方差联合检验的航迹欺骗干扰识别技术。首先分析了真/假航迹的统计特性差异,然后利用多个时刻航迹的坐标差,并通过坐标差的协方差阵对角化和归一化处理来构造检验样本,最后利用似然比统计检验的方法实现了虚假航迹的识别。仿真结果表明该技术能够对航迹欺骗干扰进行有效的识别,在雷达测距精度、测角精度变化的条件下仍能保持较高的识别率。     

利用同步测距测速资料的卫星初轨计算新方法

本文给出了利用同步测距测速资料计算卫星初轨的一种新方法,其创新之处在于: (1)改进了初值选择方式。不仅适用于任意偏心率轨道;而且精度较高,从而可显著地改善迭代收敛过程。 (2)变换了条件方程的形式,使测距数据p和测速数据p分别独立地出现在方程右端,从而可方便地消减系统误差,并可进行加权处理,有效地提高初轨计算的定轨精度。实际计算表明,该方法是可靠的。     

卫星双向法与卫星测距

卫星双向时间比对是目前远距离台站时间比对精度最高的时间同步技术,时间比对精度达几百皮秒,比GPS共视技术的时间比对精度几乎高一个数量级。中科院国家授时中心根据多台站卫星时间比对经验,提出利用卫星双向比对技术进行卫星测距(称转发器定轨)。实验证明:利用卫星双向技术(卫星需要转发器)进行卫星测距,可得到高精度卫星轨道(内符精度为几厘米)和卫星预报轨道。     

基于测距测角信息的DG-IEKF相对导航算法

在自主近距空中加油过程中,无人机通常利用机间数据链进行导航数据共享,解算获得高精度的相对导航信息.机间数据链受扰中断时,在常规相对导航策略失效的情况下,无人机通过搭载的态势感知传感器对未知环境进行探索.针对受油机与非合作目标加油机间中远距离相对导航问题,提出了一种测距测角信息下的相对状态估计算法.考虑到测距测角信息下算法的强非线性,在迭代扩展Kalman滤波(Iterative Extended Kalman Filter,IEKF)的基础上,利用信赖域狗腿(DG)优化算法,提出了一种DG-IEKF算法,并推导了该算法在迭代过程中的状态更新方程与协方差阵更新方程,最后给出了该算法的相对导航仿真结果.仿真实验结果表明,该算法导航精度优于现广泛使用的扩展Kalman滤波算法(Extended Kalman Filter,EKF)与IEKF算法,在RMSE方面与EKF相比,相对位置综合精度提高了35.55％,相对速度综合精度提高了19.20％,具有较高的可靠性与稳定性.     

通过气象卫星的单向时间传递精度可达三十毫微秒

在欧洲空间操作中心(ESOC,达姆斯塔特)的支持下,西德应用测地研究所(IfAG)和物理技术研究所(PTB)共同努力,制订了一项利用气象卫星(METEOSAT)测距信号的小规模试验计划。这种测距信号每隔3小时出现1·5分钟。在此期间,测量测距信号相对于站用时钟秒脉冲的相位。系统研究表明,可能获得的时间传递精度在30~(ns)(毫微秒)量级。接收设备包括一个2米直径的固定天线、一个低噪声宽带接收机和一个相位跟踪器和解调器,全部费用不超过20000美金。     

北斗空间信号误差统计特征及描述方法研究

通过对比北斗卫星导航系统(BeiDou Navigation Satellite System,BDS)广播星历与事后精密星历,提取了轨道和卫星时钟误差。基于北斗轨道误差及北斗卫星时钟误差统计特征分析,构建区别于全球定位系统(Global Positioning System,GPS)的BDS空间信号用户测距误差(Signal-In-Space User Range Error,SISRE)描述方法,对BDS广播星历中用户测距精度(User Range Accuracy,URA)进行了验证。6个月的北斗数据测试结果表明,北斗GEO、IGSO和MEO卫星的URA分别为3.0m、1.9m和1.6m。     

TDAS时代低地球轨道航天器的导航

九十年代将用跟踪数据采集系统(TDA5)取代现在的跟踪与数据中继卫星系统(TDRSS)。现在正在研究通过该TDAS为用户航天器提供测轨/测时功能的各种方案。TDRSS中所用的双向测距和多卜勒跟踪仍然是TDAS地基导航的一种方案,但本文集中讨论单向测距和多卜勒跟踪的方法,具体说是: (1)正向线路信标跟踪(FLBT)——在用户星上处理由TDAS卫星连续播发的独立的导航信号; (2)正向线路定期跟踪(FLST)——在用户星上处理从TDAS正向线路定期跟踪期间所接收的导航数据; (3)反向线路定期跟踪(RLST)——在地面处理从TDAS反向线路定期接收期间用户星所产生的导航数据。比较了每种方法的系统结构以及要求,给出了导航性能评价的初步结果。该性能是用户航天器轨道、TDAS星座结构和其它参数的函数。接着将这些结果与TDAS任务模型中的精度要求相比较。最后讨论了上述各种方案对TDAS和用户航天器的影响,并指出了需进一步研究的问题。     

低测角精度下的轨道确定计算方法

根据单位矢量法测轨原理,给出了在测角精度比较低或没有测角资料的情况下,利用测距、测速资料进行初轨和轨道改进的计算方法。工程实践应用表明,在测角精度比较低而测距、测速精度相对高的情况下,该方法可有效地提高轨道确定的精度。     

测距误差的群时延特性分析法及其在深空测控中的应用

分析了连续波雷达测距系统中群时延特性对测距精度的影响,采用公式和图解2种方法得到测距误差的估算方法,并结合深空测距信号进行了分析。     

航天器再生伪码测距体制分析

再生伪码测距体制通过对上行伪码测距信号进行恢复,并重新调制到下行载波发送,可以获得可观的测距信号信噪比增益。对这部分增益的合理使用,可以获得较高的测距精度,也可以获得较短的测距时间,还可以提高遥测信号的功率。本文从测距码、捕获时间以及测距信号与遥控/遥测信号之间的相互干扰3方面介绍了再生伪码测距体制。     

Space-time adaptive processing and adaptive arrays: specialcollection of papers

Space-time adaptive processing (STAP) and related adaptive array techniques hold tremendous potential for improving sensor performance by exploiting signal diversity. Such methods have important application in radar, sonar, and communication systems. Recent advances in digital signal processing technology now provide the computational means to field STAP-based systems. The objective of this special collection of papers is to examine the current state-of-the art in STAP technology and explore the remaining obstacles, practical issues and novel techniques required to implement STAP-based radar, sonar or communication systems     

The Effect of Clipping on the Performance of a Phased-Array Antenna in an Aniso-tropic Background

The effect of an anisotropic reverberation pattern on the performance of various signal processing systems for linear sonar arrays was studied. It was determined that the use of clipping at each array element could seriously affect the performance of the system in comparison on to a similar analog system.     

深空测控再生伪码测距技术研究

针对深空测控任务中低信噪比情况下的航天器高精度测距问题,对再生伪码测距技术进行论述。介绍再生伪码测距技术原理,再生伪码测距通过再生方式消除信号上行链路噪声,提高了信噪比,但需要复杂的相关器;分析再生伪码测距采用的陶思沃斯码结构,详细论述再生伪码测距信号的地面上行、星上再生、地面下行处理过程,重点介绍各处理过程中的指标条件,并对再生伪码测距进行误差分析;重点对比分析再生伪码测距与传统透明转发测距,指出前者适合于深空低信噪比条件下的高精度测距,后者适用于近地高信噪比条件下的测距。     

On cross-ambiguity properties of Welch-Costas arrays

We discuss cross-ambiguity properties of a specific family of Costas arrays called Welch-Costas (W-C) arrays. These properties are of interest in multiuser radar and sonar system, especially since Costas arrays are known to possess ideal auto-ambiguity functions. The theory of W-C arrays is reviewed. It is then proved that only pairs of W-C arrays can have at most two hits in their cross-ambiguity function (best possible case). The maximum number of hits in the cross-ambiguity functions of a family of W-C arrays is shown to be a function of the number of W-C arrays in the family. The upper bound on the number of hits in the cross ambiguity functions for a family of W-C arrays is also derived. Specific examples of how reducing the number of W-C arrays improves the cross-ambiguity properties are given for various types of prime numbers     

Passive sonar fusion for submarine C2 systems

The most important sensors for gathering target information onboard a submarine are passive sonars. Problems concerning fusion of these passive sonars are discussed. Three typical passive sonars-passive noise sonar, passive ranging sonar and acoustic pulse surveillance sonar-constitute a passive sonar system for data fusion. This paper is concerned mainly with problems of significance in system development, such as tactical application background, special fusion techniques and own-ship maneuver considerations     

非光学遥感数据的可视化处理

对非光学遥感数据进行可视化处理有利于信息的提取和识别。伪彩色处理是非光学遥感图像增强和显示的常用方法,调色板的编码技术是非光学遥感图像伪彩色显示的关键。对照灰度编码方法,给出了非线性伪彩色编码方法和类JET伪彩色编码方法,并以干涉合成孔径声纳湖试数据处理为例,验证了这些方法的有效性。     

FPGA-based military avionics computing circuits

There are processing requirements for military avionics applications in excess of 10/sup 10/ operations per second. Field programmable gate arrays (FPGAs) support these types of processing rates, and also offer other advantages (i.e., lower cost, lower power consumption, and smaller size) for military avionics relative to alternate types of processing solutions. This paper discusses the need for very high performance computing in military avionics, with precision guided munition (PGM) applications used as an example of this need. It presents a model suggesting continued rapid improvements in FPGA processing capability, and it analyzes the utility of FPGAs as processing engines in terms of processing capability, cost, power consumption, and size. It presents several examples of the use of FPGAs as processing engines which validate the model, and it also uses these examples to describe various FPGA-based processing engine implementation techniques.     

Array shape estimation tracking using active sonar reverberation

This paper concerns the problem of array shape estimation and tracking for towed active sonar arrays, using received reverberation returns from a single transmitted CW pulse. Uniform linear arrays (ULAs) deviate from their nominal geometry while being towed due to ship maneuvers as well as ocean currents. In such scenarios, conventional beamforming performed under the assumption of a ULA can sometimes lead to unacceptably high spatial sidelobes. The reverberation leaking through the sidelobes can potentially mask weak targets in Doppler, especially when the target Doppler is close to that of the mainlobe reverberation and the reverberation-to-target ratio (RTR) is very high. Although heading sensors located along the array can be used to provide shape estimates, they may not be sufficiently available or accurate to provide the required sidelobe levels. We propose an array shape calibration algorithm using multipath reverberation returns from each ping as a distributed source of opportunity. More specifically, a maximum likelihood (ML) array shape calibration algorithm is developed, which exploits a deterministic relationship between the reverberation spatial and Doppler frequencies causing it to be low rank in the space-time vector space formed across a single coherent processing interval (CPI). In this application, a sequence of overlapped CPI length snapshots of duration less than the CW pulse is used. The ML estimates obtained for each snapshot are tracked using a Kalman filter with a state equation corresponding to the water pulley model for array dynamics. Simulations performed using real heading sensor data in conjunction with simulated reverberation suggest that 8-10 dB improvement in sidelobe level may be possible using the proposed array shape tracking algorithm versus an algorithm that uses only the available heading information.     

水下声呐探测系统信息支持下的直接攻潜作战仿真

在水下声呐系统目标指示条件下,进行直接鱼雷攻潜是1种创新型战法.针对直接空投鱼雷攻潜作战问题,将水声环境信息引入鱼雷目标识别过程,建立了更为逼真的模拟法效能评估模型.仿真分析了目标定位精度,投雷参数、鱼雷搜索参数等各关键因素对攻潜作战效果的影响,提出了在水下声呐基阵目标指示直接攻潜作战时,应重点关注的若干问题.     

Automatic detection and tracking of a small surface watercraft in shallow water using a high-frequency active sonar

A high-frequency (HF) active sonar can be used to detect and track a small fast surface watercraft in shallow water based on the evolution of the watercraft wake observed in the sonar image sequence. An automatic detection and tracking (ADT) algorithm is described for this novel application. For each ping, the measurement of the target's polar position consists of 2 steps. First, the target bearing is estimated by finding the direction of arrival of the cavitation noise emitted by the watercraft. Then range measurements are extracted from the range profile (constant-angle cut of the sonar image) at the estimated target bearing. Range normalization and clutter map processing are used to reduce the number of false measurements. Estimates of the target's Cartesian position and velocity are updated at the sonar pulse repetition rate using the Kalman filter with debiased consistent converted measurements and nearest neighbour data association. The proposed algorithm is demonstrated using real data.