6.0-6.4GHz室内MIMO无线信道测量与传播特性分析

工作在6GHz以上高频段的多输入多输出(Multi-Input-Multi-Output,MIMO)无线通信系统是下一代无线移动通信的有力竞争方案.目前,对制约无线系统性能的高频段空时无线信道特性研究仍较少见.针对这一现状,采用基于网络分析仪的信道测量平台对典型办公环境下6.0-6.4GHz MIMO无线信道特性进行测量和分析.为了明确高频段为系统设计带来的新问题,将测量得到的高频段MIMO信道特性参数与低频段对比.对比结果表明,6.2GHz频段与2.45GHz频段MIMO信道传播特性存在较大差异.在对6.0-6.4GHz室内覆盖MIMO无线通信系统进行设计和评估时,需要基于6.0-6.4GHz频段无线信道传播的新特性对系统的关键技术和方案进行调整.     

无线局域网(WLAN)室外覆盖无线链路预算分析

文章介绍了无线局域网WLAN所用IEEE802.11×标准的技术特点和频率特性,分析了无线通信中上下行链路功率预算的方法,并对现行的WLAN室外覆盖系统的上下行无线链路进行了功率预算.计算结果表明:在WLAN所在的2.4GHz频段,系统上下行链路允许的最大路径损耗为120～130dB;结合WLAN所在2.4GHz频段的...     

一种新型2.4GHz频段加载贴片天线的设计

采用在贴片上开槽和加载的方法,设计了一种用于2.4GHz频段无线通信设备、内缩渐变线馈电的新型结构贴片天线.给出仿真设计的性能和多个天线样品的实测输入驻波比曲线和远区辐射特性图,详细研究分析了不同加载条件、不同辐射边尺寸对输入驻波比的影响.实测结果表明,该天线在2.4GHz频段上获得超过15%的相对带宽(VSWR<2),而且尺寸比相应频段的微带贴片天线更加微型化.     

无线射频技术在井下无线通信中的优势分析及应用

无线通信技术在煤矿的管理运营中正发挥越来越重要的作用。文中通过对现有的无线通信技术进行分析研究,确定了无线射频技术在井下应用的优势;介绍了RFID射频终端(射频卡和读卡器)的硬件构造。由于RFID通信频段的选择对其运行效果影响显著,结合煤矿井下实际的通信环境选定了2.4 GHz的工作频段。现场测试显示系统运行达到预期效果。     

2.4 GHz频段家庭电磁环境的分析和测量

对2.4～2.5 GHz频段范围内家庭的电磁环境进行了分析,给出了单个家庭住宅和多个家庭住宅的典型应用场景图.利用频谱分析仪和喇叭天线对这一频段的电磁环境进行了测量,给出了测量数据和波形,并对测量结果进行了分析和比较.还通过用户调研和电磁环境测量,对这一环境内设备间的相互干扰,尤其是无绳电话与WLAN设备间的电磁干扰情况进行了分析,并给出了初步的解决建议.     

低功耗2.4GHz无线通信系统的设计与实现

低功耗、微型化是当前无线通信产品尤其是便携产品的迫切要求。本文提出了一种工作在2.4GHz ISM频段的无线传输系统的设计方案。该方案主要采用Nordic公司最新推出的射频芯片nRF24E1,设计并实现了一种近距离、低功耗的无线通信收/发系统。     

一种小型陷波多用途超宽带天线

提出了一种小型陷波多用途超宽带微带天线。该天线与一般的宽缝隙微带天线类似,通过在矩形调谐支节上开V形缝隙获得了陷波特性。通过数值仿真和实验测量,对天线的阻抗特性、方向图和增益进行了研究。结果显示该天线在2.4到11GHz频段内驻波比小于2,在5.15~5.95 GHz范围内具有陷波特性。同时该天线还可覆盖2.4GHz无线局域网(WLAN)频段,在整个工作频段内有良好的辐射方向特性。     

基于二维LMBP神经网络的ISM频段预测算法

随着短距离无线通信技术的快速发展及应用,ISM (2.4 GHz)频段的电磁干扰问题日益凸现,而利用频谱预测来预先获知频段的占用信息,已成为解决设备间兼容共存问题的有效途径.在验证ISM频段时域频域相关性的基础上,提出了一种时频二维LMBP神经网络,并将其应用于ISM频段的频谱预测.通过仿真和理论分析得到了最佳的时频训练组合点(△t=5、f=2),在神经网络输入向量N=9的条件下,该点的预测准确度可达95％,相比Markov算法和时域LMBP神经网络分别提高了9％和4％的预测精度,且具有更优的训练收敛时间.     

2.4GHz频段无线技术标准

为了满足人们对无线通信技术的需求,现对工作于2.4 GHz（ISM）频段常用的短距离无线通信中ZigBee、蓝牙（Bluetooth）、WiFi三者的技术优势、缺点及总的市场趋势做了详细分析,证明它们的关系是既互为补充又相互竞争的。     

2.4GHz无线技术标准及ZigBee抗干扰性能

介绍了ZigBee和其他几种工作于2.4GHz ISM频段的短距离无线通信技术标准,Wi-Fi、蓝牙和无线USB,对ZigBee本身的抗干扰性能以及与其他无线技术的共存进行了分析,讨论了如何保证ZigBee避免干扰和改善其共存性能.     

煤矿井下水泵电机辐射电磁骚扰测试研究

煤矿井下由于高压、大功率机电设备众多,启停频繁,导致井下电磁干扰严重。本文针对井下电机类 设备的辐射电磁骚扰,分析了旋转电机的电磁兼容辐射发射限值,以及井下实验测试要求和方法,并对井下水泵电 机的辐射电磁骚扰进行了现场测试。测试结果表明:水泵电机在正常稳定运行时的辐射电场较弱,在整个测量频段 内没有明显的噪声突起;在电动机启停阶段,辐射电磁骚扰较强,辐射频谱达到2 GHz,主要辐射频谱在500 MHz 以 内,尤其在频段1 ~10 MHz 之内辐射电场强度达到最大。因此,煤矿井下工频电源驱动的电动机类设备的辐射电磁 骚扰主要是启停阶段产生的瞬态辐射干扰,稳定运行时辐射电磁骚扰对井下电磁环境的影响较小。     

A possible concept of how present radiated emission standards could be amended in order to protect digital communication services

Present radiated emission standards are developed to protect analog communication services. Finding a new detector for electromagnetic interference (EMI) measurements with adequate weighting properties to quantify the effect of disturbance on digital communication services, is one important issue in the evolution of present radiated emission standards in order to protect digital communication services. Recent measurement and simulation results indicated that the RMS detector exhibits a response that can be correlated to the interference impact on digital communication systems that do not use error-correcting codes, or codes of block or convolutional type. In this paper, we show that this conclusion is also valid for systems using the more complicated concatenated codes. The codes investigated so far cover a representative and relevant selection of codes employed in practical digital systems. Therefore, the proposed concept to amend existing radiated emission standards is considered valid.     

无线收发器双频ICPA的FDTD分析

高集成无线收发器的集成电路封装天线（Integrated—Circuit Package Antenna，ICPA）需要同时工作在：2．4GHz和5．25GHz的双频段上。它将微带贴片天线和射频收发器集成于一个独立的封装内，并使天线和收发器之间的电磁干扰最小。利用基于非均匀网格的时域有限差分方法（nonuniform Finite—Difference Time—Domain，nu-FDTD）对ICPA进行建模和仿真，并分析了设计参数对ICPA的影响以及ICPA的频率特性、远场辐射方向图和电磁场分布等。经过优化，ICPA天线可以准确地工作在双频段上。     

Effects of Electromagnetic Radiation From Digital Wireless Telephone Frequencies on a Double Relaxation Oscillation SQUID

In this paper, the effects of electromagnetic fields from the frequency band of digital wireless telephones on a superconducting quantum interference device (SQUID) were experimentally investigated. A first-order planar gradiometer based on the double relaxation oscillation SQUID (DROS) was operated without low-frequency magnetic shielding, and was exposed to radiated electromagnetic fields in the frequency range of 300 MHz–2 GHz. The experiments have been performed in a fully anechoic chamber to minimize reflected waves in the chamber. The flux-to-voltage transfer and the field sensitivity of the gradiometer have been observed under the irradiation of fields. Results show that the performance of the gradiometer was significantly affected at a typical power level of the digital wireless telephones for both horizontally and vertically polarized electromagnetic waves. The noise level of the DROS output voltage also increases as the strength of the external fields becomes higher.      

无线网络电磁干扰屏蔽技术及应用研究

对于普通的无线网络用户来说,无线网络的使用需要同时兼顾便携、高速和安全的特性,因此IDS是一个重要的发展方向,但对于类似军队中的保密要求更高的应用来说,则需采用更加稳妥的解决方案。TIPTOP无线网络阻断系统使用电磁干扰技术,通过对2．4GWLAN无线通信网络（802．11b／g／n）进行干扰,能够达到全部或有选择性的阻断WLAN中无线接收器（Access Point）或个人工作平台（Station）的无线信道,同时采用了智能分析技术,一旦环境中出现无线信号,即对其进行干扰,并记录干扰结果,供需要时使用。     

A parallel electromagnetic genetic-algorithm optimization (EGO) application for patch antenna design

In this paper, we describe an electromagnetic genetic algorithm (GA) optimization (EGO) application developed for the cluster supercomputing platform. A representative patch antenna design example for commercial wireless applications is detailed, which illustrates the versatility and applicability of the method. We show that EGO allows us to combine the accuracy of full-wave EM analysis with the robustness of GA optimization and the speed of a parallel computing algorithm. A representative patch antenna design case study is presented. We illustrate the use of EGO to design a dual-band antenna element for wireless communication (1.9 and 2.4 GHz) applications. The resulting antenna exhibits acceptable dual-band operation (i.e., better than -10 dB return loss with 5.3 and 7% operating bandwidths at 1.9 and 2.4 GHz) while maintaining a cross-pol maximum field level at least 11 dB below the co-pol maximum.     

雷达对扩频通信系统干扰仿真与分析

针对传统雷达电磁辐射干扰分析方法的不足,首先在时域符号级详细分析了雷达对扩频通信系统电磁辐射干扰的机理,推导得出扩频通信系统在脉冲雷达干扰下的误码率公式和曲线;然后利用建立的雷达电磁干扰仿真模型,对扩频通信系统采用不同扩频因子以及不同频率隔离度时的受扰性能进行了仿真分析,其结果与理论分析结果较为吻合。最后利用所得结论计算给出了微波频段5种典型雷达与扩频通信系统的频率-距离隔离关系。研究结果证明,本方法能在更深层次上揭示雷达辐射干扰的本质,提高频谱利用效率。     

Wireless LAN design alternatives

The authors have discussed several alternatives in wireless LAN design: media choice, operating frequency, operating mode, network topology, and access method. Although each technical choice presents both advantages and disadvantages, they argue that there is a design point that provides the best fit with present and future wireless LAN user needs. Considering all factors-including robustness, regulatory considerations, and interference avoidance-using a product based on the slow frequency-hopping spread spectrum, in the 2.4 GHz ISM band, relying on a base station remote station network topology and using a TDMA-based access method is the best way to meet the needs of radio-frequency wireless LAN users. The choices are many, but slow frequency-hopping at 2.4 GHz and TDMA-based medium access control provide the best mix of cost, range, interference, and performance     

Coexistence of 2.4 GHz sensor networks in home environment

The IEEE 802.15.4 is one of the low-layer communication standards for personal area networks(PANs) and wireless sensor networks(WSNs),which may be interfered by other wireless devices in the industrial,scientific and medical(ISM) frequency bands,especially in home environment,such as devices of IEEE 802.11b,Bluetooth,cordless telephone,and microwave oven radiation.This article examines the mutual interference effects of 2.4 GHz devices widely deployed at home,via both theoretical analysis and real-life expe...