美国高能激光武器的发展及其面临的挑战(下篇)

首先介绍了美国高能激光武器的发展战略和高层技术路线(上篇)。然后分别评述了近一年来机载战区激光武器,战术高能激光武器和机载战术激光武器,天基激光武器,地基激光反卫星武器和舰载激光武器取得的重大进展,分析和讨论了它们面临的技术挑战和可能采取的对策(下篇)。     

DFHF化学激光器喷管流动数值模拟结果

模拟得到了喉部具有不同等截面段长度的二维喷管流场 ,指出了音速线随该长度的变化规律和等截面段最佳长度。模拟分析了三种不同方法设计的喷管流场和性能参数 ,结果表明新方法设计的喷管具有合适的横向速度 ,提高了喷管对F原子“冻结”效率、纵向速度等性能参数 ;能防止喷管内边界层分离和激波产生。并根据数值模拟得到的速度分布型计算了边界层位移厚度 ,讨论了DF HF激光器上述三种喷管内边界层发展规律。     

Dead-time optimisation with reducing voltage distortion for nine-switch inverter

Nine-switch inverter with two sets of three-phase outputs is an improved topology proposed in place of the 12-switch back-to-back converters and has therefore attracted much attention in recent years. This inverter can be used with two conventional pulse width modulation approaches: different frequency and the constant frequency. One disadvantage of using this modulation method is the possibility of short-circuits in the legs (shoot-through), which decreases the reliability of converter and system. This paper presents a new modulation technique, in which switching pulses of nine-switch inverter are produced by not only the original carrier signals but also through two auxiliary carrier signals. In this method, adjustable three-phase voltages are produced in the inverter’s terminals, and so there is no possibility of any shoot-through in the inverter’s legs. The suggested reliable modulation approach does not rely on any information about the load polarity, as switching is performed by a simple and reliable algorithm. The result is the considerably better waveform quality of the output voltages in comparison with other methods. To verify the analysis, an experimental platform based on DSP is built. The simulation and experimental results are given to demonstrate the effectiveness and feasibility of this new approach.     

电磁环境监测系统分析与设计

电磁环境监测系统是复杂电磁环境构设系统的重要组成部分,主要用于监测各种通信和雷达信号,对信号进行测量,获取信号的特征参数。监测结果可为训练效果评估、动态调整电磁环境提供数据支持。介绍了电磁环境监测系统设计时监测站部署原理,监测距离、监测灵敏度和测向精度的估算方法,给出了系统的详细设计方案,包括体系框架设计和各功能子系统的实现方法,并对系统的应用性和效果进行了分析。     

基于迫零方式下带有硬件损害的大规模MIMO全双工中继系统

该文考虑一个大规模MIMO全双工中继系统,该系统下多个单天线的源节点和多个单天线的目的节点通过一个在接收端和发送端分别配置${N_{{\mathop{\rm rx}\nolimits} }}$和${N_{{\mathop{\rm tx}\nolimits} }}$根天线的中继进行通信。在非完美信道状态信息(CSI)和硬件损害的情况下,中继端在译码转发(DF)的方式下使用迫零(ZF)方法去处理接收信号和发送信号,并获得了闭合形式的接收速率表达式。根据这些表达式,可以得到各种功率收缩规律,发现随着中继端接收天线数量和发送天线数量以一定比例趋近于无穷大时,源节点的能量、中继端的能量和导频的能量可以以一定条件收缩来维持系统性能。     

氟化氘激光大气传输的定标规律

 利用激光大气传输4维程序,结合均方和半径分析方法,对氟化氘（DF）激光大气传输的定标规律进行了数值分析。得到了焦平面处63.2%环围能量半径的光斑扩展规律以及在焦平面上不同环围能量半径内的平均功率密度定标关系式。此定标关系不仅适用于大菲涅耳数、弱传输效应条件下,同时也适用于小菲涅耳数、强传输效应条件下DF高能激光大气传输,从而能够对激光大气传输的效果做出快速地预测和有效地评估。     

Power allocation-Assisted secrecy analysis for NOMA enabled cooperative network under multiple eavesdroppers

In this work, the secrecy of a typical wireless cooperative dual-hop non-orthogonal multiple access (NOMA)-enabled decode-and-forward (DF) relay network is investigated with the impact of collaborative and non-collaborative eavesdropping. The system model consists of a source that broadcasts the multiplexed signal to two NOMA users via a DF relay, and information security against the eavesdropper nodes is provided by a helpful jammer. The performance metric is secrecy rate and ergodic secrecy capacity is approximated analytically. In addition, a differential evolution algorithm-based power allocation scheme is proposed to find the optimal power allocation factors for relay, jammer, and NOMA users by employing different jamming schemes. Furthermore, the secrecy rate analysis is validated at the NOMA users by adopting different jamming schemes such as without jamming (WJ) or conventional relaying, jamming (J), and with control jamming (CJ). Simulation results demonstrate the superiority of CJ over the J and WJ schemes. Finally, the proposed power allocation outperforms the fixed power allocation under all conditions considered in this work.     

基于微分几何的平面天线阵列测向精度研究

利用阵列流形的微分几何作为分析工具,构造了实际使用中常见的平面天线阵的几何结构,并对这些阵列结构的测向精度进行了研究和全面仿真。通过比较各种天线阵几何结构的优劣,可以从中选择一种合适的、最优的阵列结构,避免设计的盲目性和随意性。这为超分辨阵列结构的选择和设计提供了一条有效的途径,在实际应用中将具有十分重要的参考价值。     

FIR数字滤波器的最优化设计及MATLAB实现

尽管窗函数法与频率抽样法在FIR数字滤波器的设计中有着广泛的应用,但两者都不是最优化的设计。介绍了一种基于等波纹切比雪夫逼近准则的FIR数字滤波器的最优化设计方法,通过MATLAB的仿真实现,证明了该方法是一种最优化的设计。     

DF/HF化学激光器HYLTE喷管的副喷管质量流量系数

 对DF/HF化学激光器HYLTE喷管的副喷管质量流量进行了数值和理论计算，得出入口滞止压力在0.01~0.4MPa之间、喉道半高度在0.1~0.9mm之间的喷管的氘气，氢气和氦气质量流量系数，总结出质量流量系数随入口滞止压力和喉道高度的变化规律，并给出拟合公式，为副喷管的设计提供依据。