小型遥测系统的容量和信道设计

论述了某型号无人机遥测系统中的容量和信道设计问题.文中对该遥测系统的组成和原理进行了介绍.结合具体的遥测任务需求,在容量设计中确定了数据传输率和使用的帧格式,在信道设计中,通过计算实际信道中的误码率,提出了相应的信道编码方案以确保数据传输的低误码率要求.     

基于NIRGAM的片上网络性能仿真

采用虫孔交换和虚拟通道技术的片上网络系统(NoC)能极大地降低传输延时,防止微片拥塞,增大网络吞吐率,从体系结构上解决了总线通信技术的瓶颈。片上网络的虚拟通道由多个缓冲区组成,其数目直接影响芯片的面积,必须通过仿真得到面积和缓冲区数目的平衡。使用NIRGAM仿真器对不同缓冲区数目的 2D Mesh片上网络进行了仿真,对其源代码中几个重要参数提出了修改建议,仿真结果表明,在本文配置的通信情况下缓冲区深度为4微片时NoC系统整体性能最好。     

一种新的基于双控制信道Ad Hoc网络媒体接入控制协议

提出了一种新的基于双控制信道的AdHoc网络媒体接入控制(MAC)协议。该协议在两个相互正交的子信道上交换RTS/CTS控制分组,解决了RTS丢失问题、死锁问题以及多信道隐藏终端问题,并提高了协议的空间复用度。实验结果表明,和已有的多信道的接入协议相比,在网络负载较重和节点密度较大的情况下,新协议提高了网络的吞吐量。     

Real-time ray-based channel generation and emulation for UAV communications

A real-time ray-based hardware emulator for Unmanned Aerial Vehicle (UAV) communication channels which suits for the Three-Dimensional (3D) dynamic scenarios and considers the movements of both terminals is developed in this paper. The time-variant channel parameters, i.e., ray delay, ray gain, and ray Doppler frequency are precalculated in the host by using the Ray Tracing (RT) method. Meanwhile, RT simulation dramatically increases the number of valid rays. To address the problem of resource limitation and huge computational burden in the implementation, an efficient ray coefficients generation method based on iteration is proposed and implemented. With the advantages of low cost and high flexibility, a Software Defined Radio (SDR) hardware platform is used to emulate the ray-based UAV channels by utilizing the compact architecture including the Time-Division (TD) scheme and Tapped-Delay Line (TDL) for channel convolution. Finally, hardware measurement results demonstrate that the properties of emulated channel, i.e., Power Delay Profile (PDP) and Doppler Power Spectrum Density (DPSD) consist with the simulated ones, which verifies the correctness of hardware implementation. The proposed channel emulator provides an efficient way for optimization, verification, and evaluation of UAV communication systems.     

空间在轨流体输运双槽道微重力实验装置

空间在轨流体输运双槽道微重力实验装置通过在微重力环境下对开口槽道中的流动进行观察,可以分析研究微重力下流体输运的稳定特性.双槽道形式的实验装置在单次实验中可同时对两种不同截面,不同流量的槽道流动进行观测,同时可有效提升落塔实验效率,减少不同槽道对比实验中的不确定因素.针对双槽道流体实验装置设计的关键问题,例如密封、压力补偿、设备布局等,提出了实验装置的系统结构及落塔实验步骤.在落塔短时微重力环境中,采用氟化液（HFE7500）流体介质,利用本实验装置成功观测到槽道流体输运流动与失稳现象.     

MEMS陀螺双通道数字接口系统设计

针对现有的MEMS陀螺接口系统只能对一个陀螺进行测控导致标定测控效率低下的问题,提出了一种新型的可同时对两个陀螺进行测控的MEMS陀螺双通道接口系统架构,并设计了一套与之对应的MEMS陀螺双通道测控电路,包括前端模拟电路、后端数字系统和人机交互终端。通过设计的人机交互系统对整个系统的全部功能进行了测试,其中扫频、锁相、稳幅、线性度和零偏稳定性等功能均能正常运行,在实际使用测试中相较于单通道接口系统测控效率提升到2倍以上。     

频率选择性衰落信道DS-CDMA无人机中继通信系统航迹规划

无人机中继通信是实现远距离无线通信的一种重要技术手段，无人机的飞行航迹对无人机中继通信系统的链路传输可靠性存在显著的影响，在频率选择性衰落信道环境下研究了基于直序列码分多址（DS-CDMA）的无人机中继通信系统的航迹优化的问题。首先，给出了基于DS-CDMA的译码转发无人机中继通信系统的模型，并理论分析给出无人机中继通信系统的链路中断概率及平均误码率计算公式，以此为基础，基于链路中断概率最小化准则提出了中继无人机的航迹规划方法，最后通过仿真验证了所提出方法的正确性与有效性。研究表明：最大比值合并DS-CDMA无人机中继通信系统可充分获取频率选择性衰落信道提供的分集增益，显著改善链路传输的可靠性。     

Development of secondary flow field under rotating condition in a straight channel with square cross-section

The developing secondary flow fields in the entrance section of a rotating straight channel were experimentally investigated using Particle Image Velocimetry (PIV). The effects of streamwise position, Reynolds number and rotation number on the development of the secondary flow fields were revealed. The results show that the absolute values of vorticity flux of the trailing side roll cells increase with increasing radius of the measured plane and rotation number. When the absolute value of vorticity flux exceeds a critical value, the merging of the trailing side roll cells appears. Moreover, when the number of the trailing side vortex pairs is even, the absolute values of vorticity flux of the leading side vortices increase along streamwise direction. Otherwise, the absolute values decrease along the streamwise direction. By the circulation analysis, this phenomenon was found to have relationship with the merging of the trailing side roll cells, and further concluded that the secondary flow field in a rotating channel has to be treated as a whole. At last, the increase of the Reynolds number was found to be able to induce the merging position moves upstream.     

强实时条件下光纤通道仲裁环带宽分配方法

光纤通道是一个为适应高性能信息传输要求而提出的计算机通讯协议,仲裁环是光纤通道的基本拓扑结构之一.为解决网络消息集实时发送的问题,研究了光纤通道仲裁环拓扑在强实时条件下的通信性能.依据实时系统中的周期任务模型和光纤通道仲裁环协议规定的访问公平机制,采用负载匹配算法提出了一种适用于仲裁环网络的带宽分配方法.推导并证明了采用该方法时在最坏情况下消息集强实时的网络可达负载率不低于50％.     

供压状态影响操纵台通道灯亮灭的机理分析

电传操纵系统通道故障灯亮灭是由监控电路根据各级表决故障信息判断产生,监控电路较复杂。飞机通电和供给液压时,通道灯时亮时灭,状态多种,是电传操纵系统故障监控电路作用的结果。阐述液压系统供压状态影响座舱ПУ-220／353操纵台通道灯亮灭的工作机理。