隧道中UHF窄带无线电波传播信道的特性

本文以在五个不同隧道中的实验数据为基础，分析了窄带ＵＨＦ无线电波在隧道中的传播特性，给出了表征空直隧道传播损耗的距离因子，并讨论了隧道中的行人、车辆及隧道弯曲度对传播特性的影响。研究表明，接收信号的慢衰落基本服从对数正态分布，快衰落在直遂道中满足Ｒｉｃｉａｎ分布，在弯曲隧道中Ｒａｙｌｅｉｇｈ分布并不能很好地模拟快衰落的分布。     

Compact Meandered Folded-Dipole RFID Tag Antenna for Dual Band Operation in UHF Range

Wireless Personal Communications - A meandered tag antenna is proposed for dual band operation in UHF (Ultra High Frequency) range at f1?=?866 MHz and...     

MIMO Channel Characterization for Short Range Fixed Wireless Propagation Environments

This paper reports results from wideband MIMO measurements performed in short range fixed wireless environments at 5.2 GHz. The objective is to provide MIMO channel characterization results for the measured environments and contribute to the limited available similar studies. Two kinds of propagation scenarios are investigated, rooftop to rooftop and street to rooftop, at three different sites always under LOS propagation conditions. The analysis of measurement data is performed in the context of non physical modeling, providing insight into the statistics of the measured channels. In particular, the slow time varying nature of the channel is studied and the narrow Doppler spectrum shape is approximated. Furthermore, frequency correlation results are obtained and the typical delay dispersion measures are extracted. Then, the antenna correlation is studied and the error of the Kronecker product approximation is evaluated. Finally, capacity results are provided and the channel measurements are characterized in terms of spatial multiplexing quality and multipath richness through condition number analysis. Nikolaos D. Skentos received his Diploma in Electrical and Computer Engineering from the National Technical University of Athens (NTUA), Greece in October 2000. Since January 2001 he has been a research associate at the Mobile Radio Communications Laboratory at the NTUA, and he is currently working towards the Ph.D. degree. His research interests include channel measurements, MIMO channel characterization, MIMO algorithms and space time processing. He has been active in the IST STINGRAY project, the COST 273 Action and the ACE Network of Excellence. He is also a member of the National Technical Chamber of Greece since 2001. Athanasios G. Kanatas received the Diploma in Electrical Engineering from the National Technical University of Athens, Greece, in 1991, the M.Sc. degree in Satellite Communication Engineering from the University of Surrey, Surrey, UK in 1992, and the Ph.D. degree in Mobile Satellite Communications from the National Technical University of Athens, Greece in February 1997. From 1993 to 1994 he was with National Documentation Center of National Research Institute. In 1995 he joined SPACETEC Ltd. where he was Technical Project Manager for VISA/EMEA VSAT Project in Greece. In 1996 he joined the Mobile Radio Communications Laboratory as a research associate. From 1999 to 2002 he was with the Institute of Communication & Computer Systems. In 2000 he became a member of the Board of Directors of OTESAT S.A. He is an Assistant Professor in the Department of Technology Education and Digital Systems at University of Piraeus. His current research interests include channel characterization and estimation, simulation and modeling for mobile, mobile satellite, and future wireless communication systems. He has been a Senior Member of IEEE since 2002, and is also a member of the Technical Chamber of Greece. In 1999 he was elected Chairman of the Communications Society of the Greek IEEE Section. Panagiotis I. Dallas was born 1967 in Thessaloniki, Greece. He obtained his diploma and Ph.D. degree from the Electrical and Computer Engineering Department of Aristotle University of Thessaloniki, Greece, in 1990 and 1997, respectively. Since 1998 he joined with INTRACOM where he currently is Section Manager of Advanced Communications Technologies branch of Emerging Technologies & Markets department, leading the next generation of broadband wireless access systems for internal and EU projects. He runs the relevant standardization activities (IEEE 802.16 and ETSI/BRAN HIPERMAN) in INTRACOM and he represents the company in WiMAX forum. Finally, he has over 30 publications in international journals and conferences. Philip Constantinou received the Diploma in Physics from the National University of Athens in 1972, the Master of Applied Science in Electrical Engineering from the University of Ottawa, Ontario, Canada in 1976, and the Ph.D. degree in Electrical Engineering in 1983 from Carleton University, Ottawa, Ontario, Canada. From 1976 to 1979 he was with Telesat Canada as a Communications System Engineer. In 1980 he joined the Ministry of Communications in Ottawa, Canada where he was engaged in the area of Mobile Communication. From 1984 to 1989 he was with the National Research Center Demokritos in Athens, Greece where he was involved in several research projects in the area of Mobile Communications. In 1989 he joined the National Technical University of Athens where he is currently a Professor and Director of the Mobile Radio Communications Laboratory. His current research interests include Personal Communications, Mobile Satellite Communications, and Interference Problems on Digital Communications Systems.     

5.8GHz短距离无线收发系统的设计

详细介绍了一个以应答芯片CHR2244为核心的5．8GHz短距离无线收发系统的设计方案。该设计将实现上行FM,下行AM的无线数据收发功能。对天线模块、射频收发模块和数据链路控制分别进行了的阐述,同时对通信过程也进行了详细的描述。     

GSM900MHz频段传播模型的校正

介绍了无线电波传播模型的作用、CW测试原理及规划软件Planet中的General模型的校正,并分析了问题区域存在的原因。     

抗振型UHF 频段功分器的研制

本文介绍了一种用于机载、弹载产品的UHF频段功分器。该功分器由集总元件构成,所用元器件均为表贴器件,具有良好的抗振性能。通过仿真软件进行设计验证,给出了仿真与实验结果,两者很好吻合。     

UHF宽带同轴-矩形波导转换器新结构

研制了一种UHF波段宽带的同轴一矩形波导转换器.这种转换器采用了新结构,它的同轴探针呈阶梯状,并在波导宽壁上配有2个调谐螺钉.经测试,转换器在490～750 MHz的频段内(矩形波导TE<,10>单模工作带宽),回波损耗低于-31 dB,在483～782 MHz的频段内回波损耗低于-30 dB.     

Narrowband Short Range Directive Channel Propagation Loss in Indoor Environment at Three Frequency Bands

Propagation loss models for indoor environment are presented. The narrowband directive channel propagation loss in indoor environment at three frequency bands namely (2.4, 3.3 and 5.5) GHz is measured. Sets of directive panel antennas are used in the measurements. RF signal generator and a spectrum analyzer are used in the measurement campaign. It is found that propagation loss is sensitive to the scenario configuration. It is noticed that the propagation loss can be modelled by a single slope propagation model or two slopes propagation model.     

基于Okumura-Hata传播模型的VHF/UHF电台位置预测研究

本文在无线电监测和VHF/UHF频段不明信号查找工作的基础上,结合新疆乌鲁木齐城区地形,通过实测数据,对VHF/UHF频段无线电信号的传播特性进行分析研究。选出适用的电波传播模型后,考虑到建筑物对电波传播的影响,引入建筑物密度修正因子对模型进行修正并验证修正模型的有效性。该研究对VHF/UHF频段无线电台位置的精准预测和查找有较大帮助。     

UHF Propagation in Caves and Subterranean Galleries

An experimental study is described on the natural propagation of UHF band radio waves in straight subterranean galleries. An extensive measurement project took place in five underground localities and, based on the experimental data, an empirical model of radio wave transmission was derived. The model was calibrated according to the measurement data and compared with the theoretical waveguide approach to propagation prediction. The presented results can be used for the practical planning of wireless communications in speleology applications and as an experimental basis for further theoretical works     

随机桥过程研究短程无线信道的空时特性

使用随机桥过程的样本建模短程无线信道中多径分量的传播轨迹。由随机桥过程的样本构造出基本随机变量,在一定的映射规则下由基本随机变量的样本得到反映无线信道空时特性的多径时延、多径信号抽头增益、多径信号的波达方向等参量。使用随机桥过程的特例布朗桥过程,分别对散射体均匀分布的信道传播环境和有约束的无线信道传播环境的空时特性进行仿真分析。仿真结果表明,在这两种传播环境中,多径分量的波达方向在仰角和水平角维度上均存在一定的局部偏好性,不满足均匀分布的假设。在仰角-水平角-多径分量到达时延这3个自由度的空间中,多径分量的分布表现出一定的规律性。     

Propagation of Wide-Band Signals at VHF/UHF

The experimental jam-resistant secure voice communications (JRSVC) system developed by M.I.T. Lincoln Laboratory was used to conduct a series of VHF/UHF (225-400 MHz) propagation measurements, representative of a veriety of tactical communications situations, both ground to ground and ground to low-flying aircraft. Results are unusual in two regards: they were made with the receiver in motion, covering many contiguous propagation paths, and the JRSVC system, by frequency-hopping over almost an octave and averaging the results, largely eliminated the effects of frequency-selective (multipath) fading that generally dominate VHF/UHF propagation measurements.     

Propagation measurements for UHF spread spectrum mobile communications

The U.S. Army is currently developing a number of spread spectrum radio systems to support its needs for more survivable and efficient mobile UHF data distribution on the tactical battlefield of the 1990's and beyond. The analysis and prediction of the performance of these systems in mobile tactical environments has been met with a great deal of uncertainty relating to the applicability of narrow-band propagation models and the effects of terrain irregularity and vegetation on broad-band signals. An overview is presented of an ongoing Army program utilizing wide-band pulse response measurements to characterize ground mobile tactical UHF spread spectrum propagation channels. Recently acquired experimental data are used to demonstrate the potential of this program for improving available tools for prediction and analysis of tactical UHF spread spectrum systems employing bandwidths of hundreds of MHz.     

V/UHF传播计算模型仿真研究

V/UHF频段在陆地和航空通信中已得到了广泛的应用.文章利用Matlab仿真平台,对自由空间中,平面大地视距路径与非视距路径上的传播损耗计算模型进行了仿真,分析得出了传播损耗与传播距离、通信频率等的关系:针对地空通信,对接收场强进行了仿真,分析得出了接收场强随发射功率、波长,通信距离、飞机高度和地面天线高度的变化关系.较为全面地仿真分析了V/UHF在陆地和地空通信中的传播特性,研究结果对V/UHF在陆地和地空通信中的应用具有一定的参考价值.     

UHF高功率固态雷达发射机

介绍了一种UHF频段高机动、高可靠的高功率固态雷达发射机的组成情况。对650 W功率组件、功放电源及过工作比保护电路的设计等进行了具体分析,对影响固态雷达发射机可靠性的因素及提高其可靠性的方法作了较深入的探讨。     

丛林对UHF频段定位系统的影响

丛林环境会引起电磁波传输的额外路径损耗(EPL)和多径,直接影响无线电定位系统的作用距离和到达时间(TOA)测量精度,也间接影响了系统的总体性能。本文分析总结了工作频率在450MHz和1100MHz附近的两种扩频定位系统在典型丛林环境下的试验数据。得出了一些共性的规律和结论。     

2.5 GHz和3.5 GHz频段的WiMAX传播模型研究与校正

本文在研究2.5 GHz和3.5 GHz理论传播模型的基础上,对2.5 GHz和3.5 GHz频段进行了无线传播模型的测试和校正,从而进一步量化分析两者间的差异,指导多频段的网络规划.     

Wide-Band UHF Radio Propagation Characteristics in a Tunnel Environment

This paper presents the measured wide-band characteristics of 900 and 1800 MHz band radio propagation channels in a tunnel environment for microcellular and personal communications. The measurements were made using the swept frequency technique. The analysis of the average measured power delay profiles reveals that the rms time delay spread is less than 25 ns when the tunnel is empty and can be as large as 103 ns when the tunnel is blocked by vehicles.     

一种星载UHF 频段小型化螺旋馈源设计

设计了一种应用于星载UHF频段小型化螺旋馈源,通过在每圈螺旋采用4个U型支节加载部分,使螺旋馈源周长变半径减小,通过减小螺距使得螺旋高度较低,与传统螺旋馈源相比,其纵向高度和径向尺寸减小了1/3和1/5,仿真和测试结果表明馈源具有良好的阻抗匹配特性和辐射特性,满足了设计要求。     

UHF 频段多层介质非等螺距标签天线*

针对RFID 电子标签的小型化和空间可压缩的要求,提出了一种新的工作于UHF 频段RFID 的非等 螺距螺旋标签天线。首先应用经典等距螺旋天线理论,探讨了非等距螺旋天线的辐射特性;然后通过分析电磁波在 不同介质层界面对辐射特性的影响,提出了多介质层填充结构,以实现多层介质标签天线,提高天线辐射效能;最后 利用CST 软件对非等距螺旋天线进行优化仿真并与实物的测试结果进行对比,二者基本吻合。实测结果表明:该介 质结构下的非等距螺旋天线在871 ~928MHz 频带范围内回波损耗优于-10dB,最大增益为2. 8dBi,3dB 波瓣宽度约 为86毅,尺寸仅为64mm×Φ6mm。