共查询到19条相似文献,搜索用时 78 毫秒
1.
2.
针对甚低频发射天线输入电抗高、输入电阻小而导致的天线Q值高、带宽窄、输入功率受限、天线系统效率低等问题,研究了伞型和T型甚低频发射天线的顶负载在不同电气连接方式下的天线输入阻抗,提出在不改变天线总体结构的情况下,改变顶负载电气连接方式可优化天线的输入阻抗的方法.计算结果和理论分析均表明,优化后的天线顶负载连接方式可降低甚低频发射天线的输入容抗、提高天线的输入电阻,从而可提高天线系统效率和功率容量、增加天线带宽,对改善甚低频发射天线性能和提高天线电气工作安全性具有重要意义. 相似文献
4.
5.
甚低频发射天线结构庞大,但其尺寸与波长相比仍属于电小天线,它的辐射电阻较小,天线的损耗电阻对天线辐射效率影响较大;天线的损耗主要来自于地损耗电阻,本文根据单极型天线地损耗电阻的理论计算公式,对设计时需着重考虑的关键参数进行了分析,并借助数值仿真计算方法对某十三塔天线的实例进行了计算验证。 相似文献
6.
7.
甚低频发射系统同步调谐研究 总被引:1,自引:1,他引:0
甚低频通信受发射天线固有带宽限制,信息速率低,为了提高甚低频通信速率,采用了不同于载频调谐的同步调谐方法,理论上分析并计算了在不同信息速率下甚低频发射机载频调谐系统和同步调谐系统的输出信号谱及信号传输效率。结果表明采用同步调谐可使天线系统在固有带宽不变的条件下提高了甚低频发射天线系统的有效带宽,从而提高了甚低频通信系统的信息传输速率和传输效率。 相似文献
8.
文中研究了甚低频发信天线电晕产生的机理,分析了电晕电压发生时伴随的物理现象和化学反应,理论推导了甚低频发射天线电晕电压的计算方法,实例给出了天线导线取值与电晕电压的计算结果,指出电晕电压与天线导线的直径、导线表面的粗糙程度、导线所处位置的大气密度、通过导线的电流频率、淋雨状态及导线的冰渍情况有关。 相似文献
9.
针对电小甚低频发射天线辐射电阻小,地损耗影响天线辐射效率的问题,文中研究了基于解析法计算分区域均匀辐射状地网区内磁场损耗电阻、电场损耗电阻和地网区外磁场损耗电阻、电场损耗电阻的方法,根据该方法可实现对分区域均匀辐射状地网的损耗电阻计算.计算结果表明,电小甚低频发射天线的磁场损耗电阻是地损耗的主要部分;此外,在地网总长度和地网敷设区域半径不变的条件下,均匀辐射状地网并不是甚低频天线的地网敷设最佳模式.基于上述结果,提出通过分区域敷设均匀辐射状地网的方法来降低地损耗电阻,为进一步提高电小天线的辐射效率提供了一种新的途径,具有一定的理论和工程实践指导意义. 相似文献
10.
11.
一般的空时编码解码时接收端需要信道状态信息(CSI),因而必须获得精确的信道估计;而差分空时编码(DSTC)接收端解码时不需要CSI,因而不需要信道估计。在信道衰落快或信息传输速率高的情况下,实时而精确的信道估计非常困难或代价很高,此时接收端不能获得CSI,因而需要差分空时编码。文章对多发射天线的差分空时编码的编译码原理、特点和性能进行了分析和比较,并对其中的部分差分空时编码给出了具体的实例和仿真结果。 相似文献
12.
13.
WIMAX系统中的多天线技术及应用 总被引:2,自引:0,他引:2
WiMAX(全球互通微波接入)技术近年来发展迅速,逐渐成为宽带无线接入技术的热点之一。WiMAX系统能够实现高于2bps/Hz的频带利用率。为了增加覆盖范围和系统的可靠性,IEEE802.16标准支持Alamouti方案的空时码(STC)、自适应天线(AAS)和多输入多输出(MIMO)技术在内的多天线技术。多天线技术的应用能显著地提高系统容量和频谱利用率,从而大大增强WiMAX技术的竞争力。 相似文献
14.
微带天线具有剖面低、重量轻、易于与平台共形等优点,传统微带天线带宽较窄,目前已有一些方法
来展宽微带天线带宽。然而,设计中发现,展宽微带天线带宽的同时可能会出现高次模,高次模的出现导致天线方
向图的恶化,而目前这方面研究还较少。本文基于线极化微带天线模型,对影响天线带宽的因素和天线高次模出现
的条件进行了分析,得到以下结论:为了增加天线带宽,应选用小介电常数的介质板,同时增加天线和反射板之间的
距离并增加天线宽度;通过对微带天线模式特性进行分析可知,若天线较宽,为了抑制高次模的出现,天线高度h 应
小于0. 15λ0 ,随着天线的变窄,这一限制逐渐变小。 相似文献
15.
16.
本电阻电容电感测试仪以AT89S52单片机为控制核心,通过测量频率来间接测量电阻器的阻值、电容器的容量和电感器的电感量,并对测试数据和测试结果进行保存记录,可调出最近十次的测量结果并显示测试的时间、元件类型、参数;所有测量的量程均能自动转换量程,并显示相应的提示语句。 相似文献
17.
By pre-equalizing inter-stream interference at the transmitter, Tomlinson–Harashima precoding (THP) algorithm provides a solution
for the downlink of multiple antenna multi-user systems, in which the decentralized structure of the receivers makes the receiver-processing
impossible. However, for the zero-forcing (ZF) THP algorithm available in the literature there are significant performance
differences between specific mobile stations. In this paper, a novel version of the THP algorithm is proposed. It greatly
improves the worst mobile's performance and ensures balanced performance of all the mobiles. For the new THP algorithm, better
performance can be obtained by suitably ordering the rows of the channel matrix. We show that the “best-first” ordering method
achieves optimal order for BER performance in systems with two mobile stations and achieves near optimal order in systems
with more than two mobile stations. Simulation is used to show the advantages of the new THP algorithm and the “best-first”
ordering method.
Jia Liu received the B.E. and M.Sc. degrees in electrical engineering from Beijing University of Posts and Telecommunications, Beijing,
China, in 1998 and 2001, respectively. Between 2001 and 2002, she worked as a system engineer in Siemens Ltd. (China), ICM
N R&D, TD-SCDMA. She is currently pursuing a Ph.D. degree at the Department of Electrical and Computer Engineering, University
of Alberta, and at TRLabs in Edmonton, Alberta, Canada. Her current research interests include broadband wireless communications,
multiple input multiple output (MIMO) antenna systems, precoding for multi-user MIMO, signal detection, and multi-user interference
cancellation.
Witold A. Krzymień received his M.Sc. (Eng.) and Ph.D. degrees (both in Electrical Engineering) in 1970 and 1978, respectively, from the Poznań
University of Technology in Poznań, Poland. He received a Polish national award of excellence for his PhD thesis.
Since April 1986 he has been with the Department of Electrical & Computer Engineering at the University of Alberta, Edmonton,
Alberta, Canada, where he currently holds the endowed Rohit Sharma Professorship in Communications & Signal Processing. In
1986, he was one of the key research program architects of the newly launched TRLabs, Canada's largest industry-university-government
pre-competitive research consortium in the Information & Communication Technology area, headquartered in Edmonton. His research
activity has been closely tied to the consortium ever since.
Over the years Dr. Krzymień has also done collaborative research work with Nortel Networks, Ericsson Wireless Communications,
German Aerospace Centre (DLR -Oberpfaffenhofen), Telus Mobility and the University of Padova (Italy). He has held visiting
research appointments at Twente University of Technology (Enschede, The Netherlands; 1980-1982), Bell-Northern Research (Montréal,
Canada; 1993-1994), Ericsson Wireless Communications (San Diego, USA; 2000), Nortel Networks Harlow Laboratories (Harlow,
UK; 2001), and the Department of Information Engineering at the University of Padova (2005).
His research is currently focused on broadband high throughput packet data access for mobile and nomadic users, employing
multi-carrier signalling, multiple antenna techniques and link adaptation, as well as on the related MAC and network layer
issues of hybrid ARQ, packet scheduling and relaying.
Dr. Krzymień is a Fellow of the Engineering Institute of Canada, and a licensed Professional Engineer in the Provinces of
Alberta and Ontario, Canada. From 1999 to 2005 he was the Chairman of Commission C (Radio Communication Systems and Signal
Processing) of the Canadian National Committee of URSI (Union Radio Scientifique Internationale). He received the 1991/1992 A.H. Reeves Premium Award from the Institution of Electrical Engineers (U.K.) for a paper published
in the IEE Proceedings, Part I. 相似文献
18.
19.
衰落余量决定链路可靠性并影响信道发射功率和用户容量的数值。本就衰落余量对cdma2000lx系统前向链路发射功率和渐近容量的影响进行了深入分析,首先介绍衰落余量概念,提出了cdma2000lx系统前向链路的发射功率和渐近容量表达式,然后通过仿真实验和数值计算给出一定条件下cdma2000lx系统前向链路的业务与导频SNR之间存在的对应关系,最后利用公式与仿真数据研究了衰落余量对前向总发射功率和渐近容量的影响。研究结果表明,cdma2000lx系统的前向总发射功率和渐近容量对衰落余量的大小十分敏感,衰落余量每增加ldB,都会引起总发射功率大幅上升,而渐近容量则迅速下降。 相似文献