Anti-follower jamming wide gap multi-pattern frequency hopping communication method

This paper deals with the follower jamming (FJ) resistance for the frequency hopping (FH) communication system over additive white Gaussian noise (AWGN) channel. Conventional FH systems are susceptible to be jammed by FJ, and multi-pattern frequency hopping (MPFH) has good resistance to FJ. To further improve the FJ rejection capability of MPFH, we propose a wide gap multi-pattern frequency hopping (WGMPFH) scheme. WGMPFH uses channels to represent messages, and the data channel and complementary channel are hopping on orthogonal frequency slots according to wide gap FH patterns. The transmitted signal lures FJ to aim at the data channel and the complementary channel is away from FJ by adopting wide gap frequency patterns. FJ does not affect the complementary channel but increases the signal energy in the data channel, thus the effect of FJ is reduced. Its bit error rate (BER) is derived under FJ and the effects of three FJ parameters (tracking success probability, jamming duration ratio and jamming bandwidth ratio) on the BER performance of WGMPFH are investigated versus the conventional FH/BFSK and MPFH system. Numerical and simulation results show that when under the worst-case FJ, the proposed WGMPFH outperforms the MPFH by about 1–3 dB and outperforms the conventional FH/BFSK by more than 4 dB. The proposed WGMPFH shows superior jamming rejection performance under FJ especially in severe signal-to-jamming ratio (SJR).     

星地非理想通道下的导航信号测距偏差分析

针对广义信道下伪码测距偏差与各部分通道测距偏差叠加值的等效性问题,研究星地叠加通道和部分通道特性对伪码测距偏差的影响,并对实际通道中伪距"分层"现象的成因展开分析。通道非理想特性会对导航信号伪码跟踪性能产生影响,综合考虑星地两端通道的非理想特性,通过对导航信号伪码跟踪函数和不同类型通道建模,研究了星地叠加通道和部分通道特性对伪码测距偏差的影响。结合几类典型星地非理想通道,利用软件接收机展开仿真验证。通过分析几类典型通道对伪码测距偏差的影响,解释了零基线双差观测量中伪距"分层"现象的成因。文中模型与相关分析方法可用于解释相关信号质量问题,并指导接收机通道的最优化设计。     

太赫兹粗糙金属目标镜面雷达散射截面预估方法

在太赫兹频段,研究金属目标表面粗糙度对雷达散射截面(Radar Cross Section,RCS)的调制作用,对粗糙金属目标的RCS缩比测量具有重要意义.通过研究太赫兹粗糙金属目标镜面RCS随粗糙度的变化规律,结合相干、非相干散射理论,在基尔霍夫近似法的基础上,提出一种特定参数区间粗糙金属目标镜面RCS的预估方法,并...     

卫星移动通信信道模型及仿真

对移动卫星通信的三种典型信道进行了完整的理论分析.通信信号在不同的信道参数条件下,经过瑞利(Rayleingh)信道、莱斯(Rician)信道和阻挡效应下的莱斯信道(Rician/Lognormal)进行了计算机仿真,得到了仿真结果.经分析比较发现,信道参数不同,得到的误码率曲线不同.信道的性能主要取决于信道参数,各种因素的影响可以归结到这些参数的影响,理论分析和仿真实验结果一致.     

AGWN信道中相关干扰对JTIDS接收机干扰效果分析

相关干扰是目前研究的对抗联合战术信息分发系统(JTIDS)比较有效的干扰样式,文中主要针对相关干扰对JTIDS接收机的干扰效果问题进行了深入研究。在建立了AGWN信道中相关干扰下JTIDS接收机模型的基础上,推导了接收机输出误比特率公式,并通过仿真和分析,得到了不同信噪比条件下接收机的最佳检测门限值以及误比特率与干信比的关系曲线,最后研究了干扰频偏对干扰效果的影响。研究表明,相关干扰对JTIDS接收机有着良好的干扰效果,并且对干扰频偏敏感。     

Information disclosure with endogenous channel structure

This article investigates the firms' optimal quality information disclosure strategies in a supply chain, wherein the supplier may encroach into the retail channel to sell products directly to end consumers. We consider two disclosure formats, namely, retailer disclosure (R-C) and supplier disclosure (S-C), and examine the optimal disclosure format from each firm's perspective. We show that either firm prefers to delegate the disclosure option to its partner when the supplier cannot encroach. However, the threat of supplier encroachment dramatically alters the firm's preference of disclosure. The supplier may prefer the S-C format to the R-C format when the entry cost is low and the disclosure cost is high to achieve a higher quality information transparency. Meanwhile, the retailer may prefer the R-C format to the S-C format when the entry cost is intermediate to deter the possible encroachment of the supplier. In this sense, the firms' preferences of disclosure format can be aligned due to the threat of supplier encroachment. The consumer surplus is always higher under the S-C format while either disclosure format can lead to a higher social welfare. We also consider an alternative scenario under which the supplier encroaches after the product quality information is disclosed. An interesting observation appears that the supplier may encroach when the product quality is low but foregoes encroachment when the product quality gets higher.     

装备环境应力归纳技术研究

对实测振动数据通过随机性检验和谱分析进行编辑确认和分离性测量分析,得到实测功率谱密度曲线;采用Arrhenius和Manson-Coffin模型对实测温度数据的周期分量和随机分量进行等效平均和等效循环处理,得到实测温度应力剖面;采用基于修正容差上限技术对实测应力进行修正,实现剖面综合,得到综合环境试验剖面。     

三角域上带多个形状参数的二次Bézier曲面片

对于三角域上二次Bézier曲面的形状调整问题,给出了带6个形状参数的拟二次Bernstein基函数。分析了该组基函数的性质,并由此组基函数定义了三角域上带形状参数的二次Bézier曲面片,该曲面片不仅具有三角域上二次Bézier曲面片的性质,而且在控制网格保持不变的条件下,具有形状可调性。形状参数具有明确的几何意义。实例表明：构造的曲面为几何造型中的曲面设计提供了有效的方法。     

浅谈高层建筑竖向疏散通道防排烟问题

烟气毒害是阻碍人员疏散和实施救援行动、致使人员伤亡的主要原因之一,因此,做好高层建筑的防排烟设计,提高防排烟系统的实际效用,有着极其重要的意义。分析了高层建筑防排烟设计的重要性,并以竖向疏散通道防排烟系统设置为例,介绍了高层建筑防排烟设计工作中存在的问题以及相应的改善策略。     

基于参数化建模的车轮形药柱形状优化

固体火箭发动机装药设计过程中,较高的装填分数往往导致药柱的应力应变较大,结构完整性不易满足要求,为了解决这一问题,将参数化建模方法与遗传算法相结合,对车轮形药柱进行形状优化.采用MSC.Patran软件的二次开发工具PCL (Patran Command Language)建立车轮形药柱的参数化有限元分析模型,能够根据...