无线通信新技术--UWB超宽带技术

UWB超宽带技术已经成为无线宽带接入技术中被关注的对象。本文对UWB超宽带技术进行了介绍,对其技术特点和技术优势进行了比较和分析,并展望了该技术在实际应用中的前景。     

UWB超宽带无线通信技术及其发展前景

本文首先介绍了超宽带技术的定义，描述了超宽带技术的特点和信道模型，阐述用于超宽带系统常用的多址方式和调制方式，给出了超宽带通信收发机结构，最后分析了国内外超宽带技术发展应用的前景。     

超宽带无线通信技术

超宽带(UWB)具有传输速率高、通信距离短、平均发射功率低等特点，非常适合于短距离高速无线通信。本介绍UWB的原理及主要技术特点，详细比较了UWB通信与IEEE 802．11、IEEE 802．15．3、Home RF和Bluetooth等技术的异同，并展望了UWB的应用前景。     

超宽带无线通信技术发展现状

超宽带通信（UWB）是近年来通信领域兴起的一种无线互连技术。UWB具有高数据率、低功耗、结构简单和价格低廉等特点．为无线通信的发展开辟了新的机遇。同时．由于其占用极宽的带宽，与其他通信系统共享频段．给干扰、兼容等相关领域的研究也带来了一定的挑战。     

超宽带无线通信技术及其应用

本文介绍了超宽带技术的基本概念、目前主要的实现方案、国际上超宽带技术的规范化和标准化工作，以及超宽带技术的应用。     

超宽带无线通信技术

近年来，超宽带（UWB）无线通信成为短距离、高速无线网络最热门的物理层技术之一。许多世界著名的大公司、研究机构、标准化组织都积极投入到超宽带无线通信技术的研究、开发和标准化工作之中。为了使读者对UWB技术有所了解，本讲座将分3期对UWB技术进行介绍：第1期讲述UWB的产生与发展、技术特点、信号成形及调制与多址技术，     

超宽带无线通信技术3

基于超宽带(UWB)技术自身的特点,UWB在短距离无线连接领域将有广阔的发展前景.目前,各大标准化组织和团体正在加紧制订基于UWB的各种技术标准.前两期主要介绍了超宽带技术的概念和基本原理、信道特征及接收机关键技术.本期为本讲座的最后一期,将介绍超宽带技术的应用前景和标准化情况.     

超宽带无线通信技术及应用研究

随着无线通信技术的发展，人们对高速短距离无线通信的要求越来越高。超宽带（uWB）技术的出现，实现了短距离内超带宽、高速的数据传输。由于其调制方式和多址技术的特点使得它具有其它无线通信技术所无法具有的很宽的带宽、高速的数据传输、功耗低、安全性高等特点。文章介绍了超带宽无线通信技术的概念、技术特点、关键技术及其在实际中的应用。     

无线多媒体接入中的超宽带技术

简要介绍了超宽带(UWB)的概念及发展过程,通过与现有短距离无线接入技术的比较,表明它在无线多媒体接入系统中具有传输速率高、空间容量大等特点,分析了尚需解决的关键技术并展望了应用前景。     

用于无线电监测的超宽带喇叭天线的研制

研制了一款用于微波频段频谱监测以及测向的,可以覆盖900MHz～11GHz的高增益超宽带喇叭天线。此款天线采用在传统喇叭天线腔体中加入一对渐变的寄生脊的方法,优化馈电部分同轴到双脊波导的转换,实现了同轴到波导的宽带匹配。最终天线实现了数十倍频程内驻波比小于2,增益在8～13dB之间,并且具有稳定的辐射方向图。     

超宽带SAR虚假图像干扰技术

为了对低频超宽带合成孔径雷达(SAR)实施有效的图像欺骗干扰,提出基于卷积技术的欺骗干扰方法。基于SAR目标回波特性,推导了干扰调制函数解析式。在产生干扰信号时,需要对解析式进行近似处理,针对低频超宽带SAR二维强耦合特性以及超宽带SAR成像处理算法,将干扰调制函数精确到三次相位项,并对各级系数进行分析和简化处理。最后通过仿真实例验证了对干扰产生函数改进的必要性及干扰的有效性。理论分析和仿真结果均表明,改进后的干扰方法可以对超宽带SAR实施有效的图像欺骗干扰。     

超宽带--下一代的无线技术

超宽带(UWB)是一项高带宽、高速、低成本和低功耗,适合在短距离无线通信的无线技术.本文介绍了UWB的概念、主要特点以及与其它短距离无线通信技术的比较,并简单分析了UWB在下一代无线通信中的应用.     

Lower bounds on lifetime of ultra wide band wireless sensor networks

The asymptotic lower bounds on the lifetime of time hopping impulse radio ultra wide band (TH-IR UWB) wireless sensor networks are derived using percolation theory arguments. It is shown that for static dense TH-IR UWB wireless sensor network, which sensor nodes are distributed in a square of unit area according to a Poisson point process of intensity n, the lower bound on the lifetime is \( \Upomega \left( {\left( {{{\sqrt n } \mathord{\left/ {\vphantom {{\sqrt n } {\log \sqrt n }}} \right. \kern-\nulldelimiterspace} {\log \sqrt n }}} \right)^{\alpha - 2} } \right) \), where α > 2 is the path loss exponent, thus dense TH-IR UWB wireless sensor network is fit to be employed in large-scale network. For static extended TH-IR UWB wireless sensor network which sensor nodes are distributed in a square \( \left[ {0,\sqrt n } \right] \times \left[ {0,\sqrt n } \right] \) according to a Poisson point process of unit intensity, the lower bound on the lifetime is \( \Upomega \left( {{{\left( {\log \sqrt n } \right)^{2 - \alpha } } \mathord{\left/ {\vphantom {{\left( {\log \sqrt n } \right)^{2 - \alpha } } n}} \right. \kern-\nulldelimiterspace} n}} \right) \), therefore large-scale extended network will lead to shorten network lifetime. The results also indicate that the lower bound on the lifetime in the ideal case is longer than that of a static network by a factor of \( n^{1/2} \left( {\log \sqrt n } \right)^{\alpha - 4} \). Hence mobility of sensor nodes can improve network lifetime.     

多媒体光纤无线宽带系统及其相关技术

采用无线链路与光纤路中频传输方式的多媒体通信网络一直是业内人士关注的焦点,它不仅可以简化基站功能,而且可以与现存的网络接线端和混合网终端连接,具有可塑性强。详细讨论和分析了多媒体光纤无线宽带系统的结构、原理及相关的技术问题。     

A new approach to peer-to-peer wireless LANs based on ultra wide band technology

The advent of Ultra Wide Band (UWB) technology offers a unique opportunity to consider a new type of peer-to-peer wireless Local Area Network (LAN) that requires neither access at a peak data rate commensurate with the full bandwidth of the medium nor a conventional medium access protocol. Rather, due to the extraordinarily high bandwidth afforded by UWB, which is typically much greater than the peak bandwidth required by any ad-hoc radio node, one might imagine a network for which pairs of nodes are interconnected by one or more dedicated (non-shared) radio channels created by time, frequency, or code division multiplexing. In this paper, we consider a network containing N ad-hoc nodes and 2N independent radio channels. Starting with (1) an N × N power matrix, where element p _i,j represents the power needed for a successful transmission from node i to node j including the effects of path loss and shadow fading, and (2) a second N × N traffic matrix where element t _i,j represents the exogenous traffic originating from node i and destined for node j, we seek to assign radio channels and multi-hop route the traffic between source-destination pairs such that the resulting connectivity pattern and traffic flow minimize the average transmit energy needed to deliver a packet between an arbitrarily chosen pair of nodes. With no medium access protocol needed, collisions cannot occur and retransmissions become unnecessary. Moreover, the available capacity grows with the number of channels created (or, alternatively, as some common set of channels are re-used on a non-interfering basis via sufficient spatial separation). In this fashion, such a UWB ad-hoc network takes on the characteristics of a multi-hop Wavelength-Division Multiplexed (WDM) network well known from the multihop lightwave network art, although the constraints and dynamics are certainly different. Since the optimum connectivity and flow problem is shown to be NP hard, several heuristics are considered and compared. These heuristics seek, first, to establish a “good” connectivity graph, and then to flow the traffic in an optimum fashion. Our results suggest that application of these techniques may provide a distinct wireless LAN advantage achievable only via UWB radio technology, and several opportunities for future work based on this novel approach to ad-hoc local area radio networks are identified and discussed. Marc Krull received his B.S. degree in electrical engineering from Brown University in 2001 and his M.S. degree in electrical engineering from the University of California, San Diego in 2004. His graduate research focused on the investigation of energy efficient routing protocols for ultrawideband networks. He is currently with Raytheon Companys Intelligence and Information Systems division in Aurora, Colorado, where he is involved in software development for satellite ground systems. Anthony Acampora is a Professor of Electrical and Computer Engineering at the University of California, San Diego, and is involved in numerous research projects addressing various issues at the leading edge of telecommunication networks, including the Internet, ATM, broadband wireless access, network management and dense wavelength division multiplexing. From 1995 through 1999, he was Director of UCSDs Center for Wireless Communications, responsible for an industrially funded research effort which included circuits, signal processing, smart antennas, basic communication theory, wireless telecommunications networks, infrastructure for wireless communications, and software for mobility. Prior to joining the faculty at UCSD in 1995, he was Professor of Electrical Engineering at Columbia University and Director of the Center for Telecommunications Research, a National Science Foundation Engineering Research Center. He joined the faculty at Columbia in 1988 following a 20-year career at AT&T Bell Laboratories, most of which was spent in basic research where his interests included radio and satellite communications, local and metropolitan area networks, packet switching, wireless access systems, and lightwave networks. His most recent position at Bell Labs was Director of the Transmission Technology Laboratory where he was responsible for a wide range of projects, including broadband networks, image communications, and digital signal processing. At Columbia, he was involved in research and education programs concerning broadband networks, wireless access networks, network management, optical networks and multimedia applications. He received his PhD. in Electrical Engineering from the Polytechnic Institute of Brooklyn and is Fellow of the IEEE and a former member of the IEEE Communication Society Board of Governors. Professor Acampora has published over 160 papers, holds 33 patents, and has authored a textbook entitled An Introduction to Broadband Networks: MANs, ATM, B-ISDN, Self Routing Switches, Optical Networks, and Network Control for Voice, Data, Image and HDTV Telecommunications. He sits on numerous telecommunications advisory committees and frequently serves as a consultant to government and industry.     

宽带对数周期天线的优化设计

通过对ＬＰＤＡ的优化设计,研制一种适合方舱结构形式车辆运载的超宽带,高增益定向天线。在研制过程中较好地解决了ＬＰＤＡ设计中常遇到的反常共振问题,实现了天线阻抗与增益在宽频带内的均衡性,以及单边平衡架设。     

Image-rejection receiver using on-chip active notch filters for 2.4-GHz band wireless communication applications

This paper presents the design and experimental results of image-rejection (IR) receiver front-end for 2.4-GHz band applications. The proposed IR-receiver front-end integrates a third-order active notch filter into each of conventional cascode low noise amplifier and down-conversion mixer to achieve high image-rejection ratio (IRR). The image signal is suppressed and the wanted signal is maximized due to series and parallel resonator effects of the notch filter, respectively. Consequently, the proposed IR-receiver front-end implemented in a standard 0.18 μm CMOS technology has the power gain of 21.5 dB, the noise figure of 3.5 dB, the input third order intermodulation product of ?15 dBm and the IRR of 56 dB. The IR-receiver front-end dissipates a total of 5.5 mA from supply voltage of 1.8 V.