基于改进CMA+MMA的直达波脉冲复包络估计技术

直达波参考信号在传输过程中经常会受到噪声、地杂波和多路径干扰的影响,造成信号失真,从而对非合作双基地雷达的性能产生影响.为了恢复脉冲制非合作双基地雷达中的直达波参考信号,考虑采用盲均衡技术重构直达波参考信号.针对直达波信号脉冲持续期间模值恒定、脉冲间歇期内模值为零的包络特性,讨论了盲均衡算法中的恒模算法(CMA)和多模算法(MMA)的特点及其应用条件,在此基础上提出了改进的CMA+MMA算法,仿真结果表明改进的CMA+MMA算法比CMA算法均衡后的互相关函数尖峰更窄,能进一步提高CMA算法对直达波脉冲的均衡性能.     

蒸发波导条件下海上搜索雷达频段选择研究

针对蒸发波导条件下海上搜索雷达频段的选择问题,介绍了电磁波传播损耗计算方法,计算并比较多个频率雷达波在各种蒸发波导条件下的传播损耗,并结合历史气象水文数据所对应的蒸发波导特征量分布规律,得出如下结论:当蒸发波导高度不超过10 m时,Ku波段传播损耗最小;当蒸发波导高度在10 m～14 m范围内时,X波段传播损耗最小;当蒸发波导高度在18 m～22 m范围时,C波段传播损耗最小.该结论对于海上搜索雷达的设计和使用具有一定的参考价值.     

基于雷达网的舰艇编队编成优化模型

为了优化舰艇编队编成,利用定性和定量分析相结合的方法,分析了影响舰艇编队雷达网作战能力的因素,建立了基于雷达网作战能力的编队综合作战能力指数模型,并在此基础上建立了舰艇编队编成优化模型.仿真结果表明,综合作战能力指数模型能够反映舰艇编队编成配置的要求以及编队装备体系效能与编队雷达网之间的关系,通过对舰艇编队雷达网的优化,进而优化舰艇编队编成.该模型对于辅助指挥员进行科学预测,合理编成编队,选择较好的配置方案,具有较好的指导意义.     

二维同步OCDMA光编码器设计与研究

文章以"同步修正素数码"为基础,利用互相垂直的两组线偏振光构造了适用于同步光码分多址(OCDMA)系统的二维光正交地址码.通过分析码字的自相关和互相关特性,确定了其选码原则.在此基础上,设计了适用于同步OCDMA系统的二维光编码器.仿真结果表明,与一维同步OCDMA系统相比,二维同步光正交地址码具有更优良的接收性能,并解决了器件在实际使用过程中可能出现的功率非线性叠加问题.     

Outage probability improvement using a conditional cooperative mechanism in heterogeneous wireless networks

The self-similarity nature of network traffic has been discovered to be a ubiquitous phenomenon in communication networks; meanwhile, heterogeneous wireless cooperative relay networks have received considerable interests in both academia and industry fields. The mechanism of cooperative relay selection is very essential for the design of heterogeneous wireless relay networks. In this paper, based on the self-similar nature of network traffic in heterogeneous wireless cooperative relay network, we propose a new relay selection mechanism called conditional relay selection which can effectively decrease the system outage probability. Compared to conventional relay selection mechanism, the proposed mechanism considers the traffic queue condition of the relay nodes rather than just comparing the signal-to-noise ratio (SNR). Through extensive comparisons with traditional cooperative relay selection mechanisms, the proposed scheme can significantly improve the system outage probability.     

An ACO and position information based intelligent QoS routing mechanism in MANET

Quality of service (QoS) routing technology, which can find the available route, is an important way to realize the end-to-end QoS provisioning for networks. Intelligent routing discovery, establishment and maintenance, which take use of ant colony algorithm, have been widely researched in the past years. But the ant colony algorithm has two obvious shortcomings, which are low convergence rate and algorithm stagnation in local optimum. As the topology of mobile ad hoc network (MANET) is always changing, the information of network status is hard to collect in time. So the enhancement of the convergence rate of the QoS routing algorithm is quite important in MANETs. Based on the AntHocNet algorithm previously designed for ad hoc networks, this paper proposes a position-based intelligent QoS routing algorithm. The position constraints are added in the procedures of tabu list forming and pheromone updating. Compared with AntHocNet, the proposed mechanism can greatly reduce the convergence rate in the premises of searching an available path with QoS guarantee according to the simulation results.     

直觉模糊集理论及其在模糊信息处理中的应用

介绍直觉模糊集(IFS)基本概念和运算及其表示形式,讨论了直觉模糊集(IFS)与Fuzzy集之间的区别和联系,回顾了直觉模糊集理论的研究进展及其在决策、近似推理领域的应用现状,最后指出直觉模糊集理论存在的一些问题和发展趋势。     

基于ARM+CPLD的UAV飞行控制系统设计

根据UAV飞行控制系统的功能任务要求,提出了一种以ARM为控制核心、以CPLD为辅助控制器件的飞行控制方案。描述了飞行控制系统总体设计方案,详细设计了飞控计算机的硬件和软件。为提高飞控系统的运算速度和精度,系统硬件采用ARM+CPLD模块设计,二者通过双口RAM进行数据交换;为满足飞控系统实时性和稳定性的要求,系统移植了μC/OS-Ⅱ实时操作系统,并根据控制功能将应用程序划分为7个任务。最后,为验证系统设计的可行性,将仿真数据和试飞数据进行了对比分析,结果表明系统设计正确、可行。     

机载雷达吊舱的结构设计

机载吊舱雷达是新的设计领域,吊舱吊挂在运输机机腹下,工作时随载机飞行,飞机对吊舱的体积、重量、外形提出了严格要求,吊舱的工作环境恶劣,其刚度和强度必须满足指标要求,以保证飞行中飞机和设备的安全。吊舱内部装载雷达电子设备系统,功能和接口众多。以某机载雷达吊舱为例介绍了吊舱结构设计应解决的关键结构技术难点,针对吊舱不同部位给出了相应的力学分析结果,为自行设计雷达吊舱进行了有益的探索。     

基于多级小波分解的复合数字水印检测技术

针对多级小波分解的复合数字水印嵌入技术,为从一个可能已经受到各种图像处理的水印图像中提取水印,提出了一种有效的复合水印提取与检测方法,可充分利用图像的能量分布特征,在高频和低频部分分别提取水印并进行检测.试验证明,该方法有效地保证水印提取的可靠性,具有较好的实用性.