无人机测控新体制研究

针对国内现有无人机测控体制的不足,将无人机测控系统抽象为几个一般性模块,对实现各个模块的多种备选方案进行综合分析与比较,选用其中适应无人机测控环境并且优势突出的备选方案作为新体制的内容,同时在新体制中加入加密模块.理论分析表明,新体制能够有效提高无人机测控系统信息传输的有效性与可靠性.     

空战机动决策中的影响图方法

首次将影响图分析方法引入到一对一空战机动决策中。在影响图模型中,各种空战态势下的每个备选机动方案都与一个概率值和一个效用值相联系,根据贝叶斯定理可以利用传感器信息降低结果的不确定性,影响图分析为综合效用值提供了概率分布,表示完成各备选动作的成功率,最终的决策根据所选的决策标准而定。最后进行灵敏度分析以决定各因素对决策结果的影响程度。     

基于功率分配能量采集的全双工放大转发中继系统

针对三节点放大转发中继系统,研究了基于功率分配能量采集的全双工中继传输方案。在中继配置大规模天线的情况下,提出了三种天线选择方法,并通过合理的假设分别推导了三种天线选择方法的速率的近似闭合表达式,并设计了天线选择模式切换方案。基于三种不同的天线选择方法,该文分析了基于功率分配采集协议中的最优功率分配因子以及不同方案的算法复杂度。最后,通过蒙特卡洛仿真证明了闭合表达式的准确性,并基于发射功率和信道增益分析了三种方案的优缺点。其中在大发射功率的情况下,方案一的性能最优;在小发射功率的情况下,方案二的性能最优;在中等发射功率的情况下,折中的方案三的性能最优。      

国外数字电视技术发展与标准化动态报道

随着《推进三网融合的总体方案》和第一批12个试点城市名单和试点方案的公布,我国的三网融合已经进入实质性推进阶段。CCBN2011将＂推进三网融合、共创广电未来＂作为主题,反映了当前广电行业的工作重点,     

新一代宽带通信卫星系统网络同步方案

网络同步是卫星通信系统的关键技术。针对基于MF-TDMA／TDM体制的新一代宽带多媒体通信卫星系统,提出了网络同步的总体方案;在此基础上,分别设计了上下行链路的帧同步结构和信号流程,并对捕获、失同步后的快速恢复和定时控制方案等关键问题进行了探讨。     

一种时分单通道自适应天线的研究

提出了自适应天线系统的一种时分单通道接收机方案,针对HF三元阵列自适应零位天线系统,分析了其帧结构、采样周期、时隙及其与载波之间的关系.给出了直接利用采样数据计算相关矩阵的算法.解决了多通道接收机电路复杂,难以保证各通道性能一致的问题.模拟测试结果证明了该方案可对两个任意来向的干扰进行有效的抑制.     

大规模无线局域网规划设计研究

本文介绍了大规模无线局域网系统设计领域的研究现状,归纳了网络设计初期要解决的三个问题:用户需求分析、拓扑结构和协议标准,阐述了网络设计流程的四个阶段:服务区网格划分、接入访问点备选位置初定、接收信号强度测量、接入访问点放置和信道配置.     

综合布线系统(六) 第六讲 综合布线系统工程总体方案设计

系统地介绍了智能化建筑和智能化小区的综合布线系统工程总体方案设计，重点说明了网络结构、设备配置、管槽系统以及连接方式等。概述了智能化小区的基本功能和智能化住宅建筑（家居）系统的典型布线方案。     

武装直升机综合显示系统ATS总体方案顶层设计

针对采用纯硬件专用测试设备等传统检测手段和方法来测试某新型武装直升机综合显示系统所存在的多方面缺点,在研究武装直升机综合显示系统结构组成及工作原理的基础之上,根据设计基本原则进行自动测试系统硬件和软件的需求分析,提出一套自动测试系统顶层设计总体方案.采用"工控机 适配器"组合方案搭建自动测试系统的硬件构架,运用层次分析法挑选工控机和各总线模块等众多现成商用产品.设计测试软件的层次化结构,提供软件开发关键问题的解决方案.     

平面双频单极天线研究

研究了一种小型化的平面双频天线,利用一个斜F加倒L图形结构并通过在天线结构中的电感平衡加载来设计一种平面单极双频天线.它具有接地板小且天线低端谐振点频带宽的特点,为平面双频单极天线的小型化设计提供了一种新的方案.     

具有天线选择与中继选择的空间调制技术

针对空间调制(SM)技术存在的缺欠,提出了具有天线选择和中继选择的空间调制系统方案。首先在多输入多输出(MIMO)信道模型下,通过对发送端天线选择,将拥有最佳信道状态的天线选出进行SM,打破SM技术对发送端天线数的限制,并提升采用高阶调制的SM分集性能。然后进一步将此思想引入协作通信网络,结合传感器网络的分级观念,提出采用中继选择和空间调制的中继传输协议,并通过仿真观察系统分集性能的改善。仿真结果表明,上述中继传输协议不仅能提升系统性能,而且使系统配置更加灵活。     

拥有多天线源节点的放大转发双向中继信道机会中继策略研究

We consider a two-way relay network where the Amplify-and-Forward (AF) protocol is adopted by all relays in this paper. The network consists of two multi-antenna source nodes and multiple distributed single-antenna relays. Two opportunistic relaying schemes are proposed to efficiently utilize the antennas of the source nodes and the relay nodes. In the first scheme, the best relay is selected out by a max-min-max criterion before transmitting. After that, at each source, only the antenna with the largest channel gain between itself and the best relay is activated to transmit and receive signals with full power. In the second scheme, assisted by the best relay which is selected by the typical max-min criterion, both source nodes use all their antennas to exchange data, and match filter beamforming techniques are employed at both source nodes. Further analyses show that all schemes can achieve the full diversity order, and the conclusions are not only mathematically demonstrated but numerically illustrated. System performance comparisons are carried out by numerical methods in terms of rate sum and outage probability, respectively. The beamforming assisted scheme can be found to be superior to the antenna selection scheme when accurate Channel State Information (CSI) is available at the transmitters. Otherwise, the latter is very suitable.     

Improved generalized spatial modulation via antenna selection

When a high spectral efficiency is needed, the cost of Euclidean distance‐based antenna selection for spatial modulation (EDAS‐SM) in terms of hardware, size, and computational complexity is significantly increased because of the large transmit antenna array required. In comparison, generalized spatial modulation (GSM) can match the spectral efficiency of EDAS‐SM, while using significantly fewer transmit antenna elements. However, the error performance of GSM is naturally limited because of the use of a predetermined and fixed set of transmit antenna combinations. By exploiting knowledge of the channel, the optimal set of transmit antenna combinations can be selected by maximizing the minimum Euclidean distance between transmit vectors. In this paper, an adaptive scheme for selection of the optimal set of transmit antenna combinations is proposed to improve the reliability of GSM. The computational overhead of the said scheme is relatively high; hence, a low‐complexity suboptimal scheme for selection of the set of transmit antenna combinations is further proposed. The improved GSM schemes address the spectral efficiency limitation of EDAS‐SM, while demonstrating superior error performance.     

利用双天线干涉检测针对SAR的欺骗干扰

该文根据欺骗干扰原理,将动目标检测技术引入到对欺骗干扰目标的检测中,提出了沿航迹双天线干涉对消检测欺骗干扰的方法。并在空域对消技术的基础上,进一步提出了跨航迹双天线干涉对消检测欺骗干扰的方法。文中分别对这两种检测方法中的空域对消技术做了详细的分析,对检测方法的适用性进行了讨论。最后利用点目标进行了仿真实验,结果表明这两种方法都能对欺骗干扰目标进行有效的检测与识别。     

Optimum scheduling for smart antenna systems in Rayleigh fading channels

Optimum and suboptimum scheduling schemes are proposed in the uplink of array antenna systems. We assume that once a user is permitted to transmit the data, the user transmits the data using the maximum power, and adjusts the transmission bit rate so that the energy-per-bit-to-interference-plus-noise-density ratio should be equal or higher than a threshold. In this system model, we consider an optimization problem: How many and which users should be selected to transmit their data at a time in order to maximize the throughput? Based on the analysis on the complexity of the optimum scheme, we propose another optimum scheme having reduced complexity. To reduce the complexity further, we also propose three suboptimum scheduling schemes by limiting the number of users simultaneously transmitting, by choosing the users with higher channel gains, and by partitioning a cell into multiple parts. In circular and linear arrays, the performance results of all the proposed schemes are presented and compared.     

Adaptive transmit antenna selection with pragmatic space-time trellis codes

We consider the problem of selecting a subset of transmit antennas in MIMO systems to minimize error probability when only partial channel information is available at the transmitter. An upper bound for error probability of space-time coded transmit antenna selection scheme conditioned on the channel state information is presented. Based on the performance analysis, a criterion of selecting a subset of available transmit antennas to minimize the upper bound on the PEP is proposed. In contrast to other transmit antenna selection schemes for uncoded transmission or with a fixed number of antennas within the selection subset in the literature, the proposed scheme can adaptively select both a variable number of transmit antennas and their corresponding space-time codes for transmission. Furthermore, we present pragmatic space-time trellis coding schemes for slow Rayleigh fading channels. The principal advantage of the schemes is that a single encoder and decoder can be used for systems with a variable number of transmit antennas. The performance of the pragmatic space-time codes with adaptive antenna selection and the effect of the imperfect channel estimation on performance are evaluated by simulations. It is shown that the adaptive selection offers considerable antenna selection gain relative to the antenna selection system with a fixed number of antennas within the selection subset     

Robust Transmit Antenna Selection with Phase Feedback Over Correlated Fading Channels

A new transmit antenna selection (TAS) scheme with phase feedback for multiple-input multiple-output systems is proposed in this paper. This scheme allows two or more transmit antennas to simultaneously use one radio frequency chain. By grouping the transmit antennas according to their similarities in instantaneous channel coefficients into two subsets and treating each subset as a single antenna, both hardware complexity reduction and antenna array gain can be achieved. Compared with the transmit antenna selection combined with space-time block code (TAS/STBC) scheme, the proposed TAS scheme provides excellent robustness, in terms of symbol error rate performance, against spatially correlated fading channels. Moreover, the proposed TAS scheme need not use STBC encoder and decoder which used in the TAS/STBC schemes. Therefore, the proposed TAS scheme is simpler than the TAS/STBC schemes in practical hardware implementation.     

一种基于HARQ反馈的切换合并发送分集技术

本文提出了一种与HARQ相结合的天线选择发送分集方案,该方案利用HARQ的ACK/NAK信号作为天线选择指示,如果反馈ACK则继续使用当前天线,否则切换到下一个天线.仿真表明,在低速情况下,新方案相比单天线系统有显著的分级增益,与传统的选择分集相比,能节约反馈,简化系统,同时性能损失不大.     

某雷达自动调平机构的设计分析

某雷达在作战前需要进行雷达车的架设调平工作，采用电动自动调平是一种快速可靠的调平方法。它同以往的手动，液压传动调平相比有许多优点：如调平时间短，调平精度高，可靠性高等。本文着重就调平机构的结构设计进行分析，探讨其系统的高效性和可靠性。