雷达极化检测器性能对比分析

该文在建立极化雷达杂波和目标回波模型基础上,采用蒙特卡洛仿真方法,对比分析了最佳极化检测器(OPD)、极化白化滤波器(PWF)、最佳张成检测器(OSD)、极化匹配滤波器(PMF)、功率最大综合检测器(PMSD)和单通道检测器(SCD)的理想检测性能,同时,结合各极化检测器的检验统计量,分析了各自的实现难易度.分析结果表明,PWF、OSD和PMSD理想检测性能较好,且较易实现.考虑到工程应用中,PWF、OSD需要杂波协方差先验信息,基于杂波协方差及其关键参数估计,文章进一步对比分析了PWF、OSD和PMSD的自适应检测性能.结果表明,当观测次数大于64时,PWF自适应检测性能最好.     

一种面向输出响应的多频测试故障检测与隔离方法

介绍一种在测点访问有限的情形下 ,针对模拟电路外接口的响应信息进行故障检测和隔离的方法。在构建连续的故障字典曲线的基础上 ,通过仿真实验 ,探讨并验证了利用多频测试来积累故障误差 ,构建误差曲线以检测和判别故障器件的实现思路。     

基于周期图法的残留载波BPSK信号检测

讨论高斯白噪声背景下基于周期图法的残留载波BPSK(RC-BPSK)信号的检测问题。标准周期图法在正弦信号检测中的性能最优,但是在RC-BPSK信号检测中的性能却不佳;能量检测法只在信噪比很低的情况下性能较好;在信噪比较高时,虽然Bartlett法有较好的性能,但需要分段多次计算周期图,不利于与其他检测方法配合使用。文中在频谱匹配法的基础上发展了一种频谱相关检测方法,仿真结果表明该方法可以获得和Bartlett法相似的性能,同时只需要计算一次周期图。     

一种多载波情况下的微放电检测新方法

文章基于航天器无源产品在二次电子倍增微放电过程中,多载波信号通过会在近载波产生互调产物这一机理,介绍了在多载波情况下,用检测近载波互调产物变化来检测微放电的新方法。依据无源互调的幂级数非线性分析方法,建立双载波线性模型加以分析,说明距离载波较近的三阶互调产物的功率变化比载波功率变化快,提供了这种检测方法的理论依据,最后用实验结果验证了此方法。     

高轨目标监视系统星座设计和探测效能分析

针对高轨目标编目与成像的应用需求,提出一种运行于亚同步轨道、兼具对同步带目标远距离探测编目和近距离成像侦察的高轨天基星座。根据同步带目标探测编目要求,推导和分析了星座的轨道部署和光学相机扫描方式对目标探测效能的影响,确定了顺行轨道的双星星座可行解更多,综合探测效能更高。设计了一种符合顺光观测约束的姿态导引律,结合可行解中选取一组解进行仿真,结果表明：在夏至和秋分两种工况下,采用顺行轨道的双星星座,可对轨道倾角不大于相机半视场的所有同步带目标进行无缝遍历,且每天的探测次数不小于4次,观测弧长不小于1分钟,与理论推导一致。     

非高斯杂波背景中的两个距离扩展目标检测器

针对采用球不变随机向量(SIRV)建模的非高斯杂波背景中检测具有稀疏散射点的距离扩展目标问题,先假设目标强散射点的位置信息已知,采用广义似然比检验(GLRT)理论,提出了基于散射点位置的GLRT (SL-GLRT) 检测器。然后,采用门限法估计散射点的位置信息,提出了双门限恒虚警率(DT-CFAR)检测器,推导了虚警概率与检测门限关系的解析表达式,并给出门限的确定方法。与现有方法相比,散射点位置信息已知时, SL-GLRT 具有最佳的检测性能,散射点位置信息未知时,DT-CFAR具有较好的鲁棒性。     

基于检测前跟踪的超视距雷达微弱目标检测方法

天波超视距雷达（over-the-horizonradar,OTHR）通过快速傅立叶变换（FFr）实现相干积累,再利用常规的方法进行目标检测。但这种方法在弱目标、低信噪比的情况下效果并不好。本文提出了一种基于检测前跟踪（track-before-detect,TBD）的OTHR弱目标检测方法,利用数学形态学对每帧弱目标回波信号进行滤波,再通过动态规划方法进行检测。仿真结果表明,该方法能够有效地提高OTHR对弱目标的检测能力,运算效率高,实用性强。     

DebrisWatch I: A survey of faint geosynchronous debris

Recent anomalies exhibited by satellites and rocket bodies have highlighted that a population of faint debris exists at geosynchronous (GEO) altitudes, where there are no natural removal mechanisms. Despite previous optical surveys probing to around 10–20 cm in size, regular monitoring of faint sources at GEO is challenging, thus our knowledge remains sparse. It is essential that we continue to explore the faint debris population using large telescopes to better understand the risk posed to active GEO satellites. To this end, we present photometric results from a survey of the GEO region carried out with the 2.54 m Isaac Newton Telescope in La Palma, Canary Islands. We probe to 21st visual magnitude (around 10 cm, assuming Lambertian spheres with an albedo of 0.1), uncovering 129 orbital tracks with GEO-like motion across the eight nights of dark-grey time comprising the survey. The faint end of our brightness distribution continues to rise until the sensitivity limit of the sensor is reached, suggesting that the modal brightness could be even fainter. We uncover a number of faint, uncatalogued objects that show photometric signatures of rapid tumbling, many of which straddle the limiting magnitude of our survey over the course of a single exposure, posing a complex issue when estimating object size. This work presents the first instalment of DebrisWatch, an ongoing collaboration between the University of Warwick and the Defence Science and Technology Laboratory (UK) investigating the faint population of GEO debris.     

Improved detection of faint streaks based on a streak-like spatial filter

This paper presents an algorithm to detect very faint object streaks on CCD images acquired with an optical system. The proposed detection method uses image filters simulating the geometrical form and orientation of possible streaks on the CCD image. The method searches for a matching between streak and filter evaluating the convolutions of the image with all possible filters. Based on the statistics of the image background a threshold is applied in order to accept, respectively reject, the possible streak candidates. The detection probabilities and the effect of different parameter settings are estimated with tests on simulated images, while subframes of real images are used to evaluate the applicability of the algorithm to real cases. The detection probability of this method depends on the length and on the signal-to-noise ratio of the streak. For long streaks, a detection for signal-to-noise values around 0.5 is achieved. The further characterization of the detected streak (e.g. centroid and length), which is not performed in the current algorithm, and the reduction of the computation time, which is relatively high for full acquired frames, as well as possible improvements are briefly addressed.     

基于单片机控制的经济型车床闭环数控系统

为了满足传统车床的数控改造的需要，本文提出了一种基于单片机控制的车床数控系统，给出了系统硬件的构成方案及软件结构组成。本系统精度高，功能强、价格低，可靠性好。