Very high energy gamma-ray sources

A brief review of very high energy gamma-ray astronomy achievements is presented. The results of observations of the Crab nebula, the Cygnus X-3, Vela pulsar, radiogalaxy Centaurus A and 2CG 195+4 show that all these objects are the sources of very high energy gamma-quanta. The most powerfull source is Cygnus X-3. Its gamma-ray luminosity is no less than 3·10³⁷ erg.s⁻¹. The upper limit of quanta energy is no less than 10¹⁶eV. All sources are variable in different time scales, from milliseconds up to years. The nature of all these sources is not known yet, but known ones are pulsars.     

Investigating the Coronal Mass Ejections associated with DH type-II radio bursts and solar flares during the ascending phase of the solar cycle 24

We studied a set of 74 CMEs, with shedding the light on the halo-CMEs (HCMEs), that are associated with decametric – hectometric (DH) type-II radio bursts (1–16?MHz) and solar flares during the period 2008–2014. The events were classified into 3 groups (disk, intermediate, and limb events) based on their longitudinal distribution.We found that the events are mostly distributed around 15.32° and 15.97° at the northern and southern solar hemispheres, respectively. We found that there is a clear dependence between the longitude and the CME’s width, speed, acceleration, mass, and kinetic energy. For the CMEs’ widths, most of the events were HCMEs (～62%), while the partial HCMEs comprised ～35% and the rest of events were CMEs with widths less than 120°. For the CMEs’ speeds, masses, and kinetic energies, the mean values showed a direct proportionality with the longitude, in which the limb events had the highest speeds, the largest masses, and the highest kinetic energies. The mean peak flux of the solar flares for different longitudes was comparable, but the disk flares were more energetic. The intermediate flares were considered as gradual flares since they tended to last longer, while the limb flares were considered as impulsive flares since they tended to last shorter.A weak correlation (R?=?0.32) between the kinetic energy of the CMEs and the duration of the associated flares has been noticed, while there was a good correlation (R?=?0.76) between the kinetic energy of the CMEs and the peak flux of the associated flares. We found a fair correlation (R?=?0.58) between the kinetic energy of the CMEs and the duration of the associated DH type-II radio bursts.     

机载综合无线电平台的中频数据传输总线优选分析

在综合无线电平台中，根据硬件平台通用化要求，需要选择一种总线同时满足CNI 不同波形的中频 数据传输对延时、带宽和误码率的要求。本文针对不加协议的GTX 和加上高速串行通信协议的Aurora、SRIO 进行测试，得到这三种高速串行总线在延时、带宽和误码率的对比分析，从而选择一种总线作为多波形综合的 中频数据传输总线。     

Direction finding for two-dimensional incoherently distributed sources with Hadamard shift invariance in non-uniform orthogonal arrays

This paper proposes a novel algorithm for Two-Dimensional (2D) central Direction-of-Arrival (DOA) estimation of incoherently distributed sources. In particular, an orthogonal array structure consisting of two Non-uniform Linear Arrays (NLAs) is considered. Based on first-order Taylor series approximation, the Generalized Array Manifold (GAM) model can first be established to separate the central DOAs from the original array manifold. Then, the Hadamard rotational invariance relationships inside the GAMs of two NLAs are identified. With the aid of such relationships, the central elevation and azimuth DOAs can be estimated through a search-free polynomial rooting method. Additionally, a simple parameter pairing of the estimated 2D angular parameters is also accomplished via the Hadamard rotational invariance relationship inside the GAM of the whole array. A secondary but important result is a derivation of closed-form expressions of the Cramer-Rao lower bound. The simulation results show that the proposed algorithm can achieve a remarkably higher precision at less complexity increment compared with the existing low-complexity methods, which benefits from the larger array aperture of the NLAs. Moreover, it requires no priori information about the angular distributed function.     

宇宙噪声的电离层闪烁与电离层不规则结构的结构参数

利用宇宙噪声是均匀的。各向同性的背景电磁辐射的假设,对电子密度涨落空间分布波数谱为负幂律函数的电离层不规则结构,用射线光学方法导出了闪烁功率谱的表示式。与射电星和轨道人造卫星信标的电离层闪烁相比,减少了因相对运动弓队的变量。用数值计算方法研究了电离层不规则结构的结构参量L_y、l_y、p、η对功率谱的影响。与实测资料比较,发现电离层吸收事件期间且Riometer记录的闪烁资料中,60%以上相应的不规则结构有L_y>103,η>η₀(0.2<η₀<0.5).      

基于卷积盲分离的强干扰下通信信号分离算法

针对目前通信辐射源个体识别算法在实际试验中由于各类干扰信号和多径衰落导致识别率较低的问题,提出一种用于识别算法前端的信号分离算法,可有效地减少其他电磁信号对于识别算法输入信号的影响,从而提高在复杂电磁环境中通信辐射源个体识别的正确识别率。该算法将灾变策略和搜索状态的自适应引入量子粒子群算法,通过对混合信号的联合对角化从截获的观测信号中提取出目标通信辐射源的有用信号。为了更加系统、直观地衡量算法的分离效果,提出分离熵来量化算法的整体性能。仿真结果表明,该分离算法可以把目标通信辐射源的有用信号从复杂电磁环境中提取出来,从而提高通信辐射源个体识别在复杂电磁环境中的正确识别率,具有较好的可行性和有效性。     

脉冲多卜勒引信实时校准技术初步研究

脉冲多卜勒引信实时校准技术主要对引信回波模拟源的无线电引信技术指标进行准确评定,以达到校准的目的。目前对该类专用测试设备的校准仍停留在分项校准的状态,无法全面地对整个专用测试设备进行评定,本文利用"宽带数字接收+软件无线电"技术和解调算法,实现对引信回波模拟源的系统级校准的目的。     

陆基超远程无线电导航发展研究

定位导航和授时(PNT)系统是保障现代社会正常运转必不可少的基础设施,为了提供可靠的PNT信息服务,需要研发不依赖于卫星导航的PNT系统。介绍了国内外陆基超远程导航系统的发展情况,提出了发展基于甚低频无线电信号的陆基超远程无线电系统架构、关键技术及发展建议,陆基超远程导航系统可以在卫星导航不可用时提供备份,对于构建冗余可靠的国家PNT体系、保障PNT信息的安全及可靠性具有重要意义。     

联合截获威胁下的雷达射频隐身目标搜索算法

针对基于射频(RF)隐身需求的机载雷达目标搜索问题进行了研究。通过分析实际作战中射频辐射面临的截获威胁,提出了一种基于联合截获威胁的射频隐身性能表征方法,并给出了具体的值估算方法;对机载雷达搜索任务中辐射参数的优化问题进行了建模,并采用优化算法对目标函数进行求解。通过分析典型情景下解集的分布特点,给出了从最优解集中选取最终解的方法。结果表明,提出的射频隐身性能表征方法能更好地反映截获实现过程的多域需求,提出的雷达搜索方法能够在保证探测性能的同时,提高射频隐身性能和搜索速度,能够为相控阵雷达搜索任务中参数的优化控制提供方法和依据。