The Research of Smart Antenna Technique for McWiLL Broadband Wireless Communication System

合集下载

人工智能技术在生命科学中的应用研究

人工智能技术在生命科学中的应用研究

人工智能技术在生命科学中的应用研究Chapter 1: Introduction人工智能技术在生命科学中的应用研究The advancement in technology has marked a milestone in the field of science and healthcare. Among the latest technologies, Artificial Intelligence (AI) has shown promising results in the field of life sciences. The integration of AI with biology has led to the emergence of a new field known as bioinformatics. The application of AI techniques in bioinformatics has enabled researchers to analyze complex biological data sets and provide insights into various aspects of life sciences. In this article, we will discuss the application of AI technology in life sciences and how it has revolutionized the field.Chapter 2: Overview of Artificial Intelligence人工智能技术在生命科学中的应用研究Artificial Intelligence, commonly known as AI, refers to a machine's ability to learn and make decisions independently without human intervention. It is a branch of computer science that involves the development of algorithms that allow machines to imitate human cognitive abilities. Some of the commonly used AI techniques include machine learning, deep learning, natural language processing, and computer vision. These techniques enable machines to makepredictions, classify data, and recognize patterns. The application of AI techniques in life sciences has brought considerable changes.Chapter 3: Application of AI in Life Sciences人工智能技术在生命科学中的应用研究The application of AI in life sciences has extended to various areas, including drug discovery, genomics, proteomics, and disease diagnosis. AI algorithms can analyze large amounts of biological data, identify trends, and provide insights that traditional methods find difficult to produce.Drug Discovery: AI has played a critical role in the exploration of new drugs. It enables researchers to analyze data to identify potential targets for drug development, thus speeding up the process. AI algorithms can predict the potential efficacy of a compound, reducing the cost and time of clinical development.Genomics: AI techniques can analyze large genomic data sets to understand the relationships between genes and the development of diseases. AI algorithms can identify mutations and genetic variations that contribute to disease, and predict an individual's likelihood of developing a particular disease.Proteomics: AI can identify and classify proteins in biological samples such as blood and tissue. Accurate protein identification is crucial for drug development and disease diagnosis.Disease Diagnosis: AI algorithms can analyze medical images and identify abnormalities that may be difficult for doctors to identify. AI-powered diagnosis tools can improve accuracy and efficiency in disease diagnosis.Chapter 4: Future Directions人工智能技术在生命科学中的应用研究The application of AI in life sciences holds a lot of potential, and there are several areas where researchers can explore in the future. One of the promising areas in which AI can be applied is personalized medicine. AI algorithms can predict an individual's response to a particular treatment, thus providing personalized treatment options. Another area of interest is the development of new drugs that target specific proteins, such as cancer cells.Furthermore, AI algorithms can be used to develop predictive models that can anticipate the evolution of diseases such as Alzheimer's and Parkinson's. This can enable doctors to diagnose diseases before symptoms appear and prevent their progression.Chapter 5: Conclusion人工智能技术在生命科学中的应用研究The application of AI in life sciences is rapidly growing, and it has the potential to revolutionize the field. The integration of AI with biology has enabled researchers to analyze complex biological data setsand provide insights that traditional methods find difficult to produce. The future of life science research looks promising, and it is essential to continue exploring the potential of AI to unlock new possibilities in the field.。

手机移动定位系统的设计与实现优秀毕业论文 参考文献 可复制黏贴

手机移动定位系统的设计与实现优秀毕业论文 参考文献 可复制黏贴

硕 士 研 究 生:曹伟

师:李斌教授
副 导 师:蒋纯波工程师
申 请 学 位:工程硕士
学 科 、 专 业:软件工程
所 在 单 位:软件学院
答 辩 日 期:2006 年 6 月
授 予 学 位 单 位:哈尔滨工业大学
Classified Index:TP319 U.D.C.: 621.3
Dissertation for the Master’s Degree in Engineering
本课题针对在移动通信系统中对手机进行定位的特征基于普天信息技术4哈尔滨工业大学工程硕士学位论文研究院高可用电信级业务应用开发平台应用移动定位技术实现对手机的定位不仅能够实现对手机的定位而且还能减少定位的时间以及提高定位的精章绪论简要描述课题的来源背景及研究目的以及与手机移动定位系统相关的国内外研究现状
哈尔滨工业大学工程硕士学位论文
services applications development platforms of institute of Putian, this paper introduces how to design and realization the mobile phone positioning system, design and realize the system functions by using programming languages. This paper give the result of testing in the actual network environment in order to verify the system performance. Keywords mobile communication network, mobile position, mobile phone

电气工程及其自动化英语介绍

电气工程及其自动化英语介绍

The electrical engineering fastens of automation profession introductionAutomating the professional development can be engaged in electrical engineering and it automates related realm to work of, special feature fresh clear compound type deluxe engineering technique talented person, particularly for pay attention to a student to obtain to know the development of ability and overall character of knowing. The professional graduate student adapts to ability strong, employment noodles breadth, employment rate Gao, the three years employment rate attains 100%.Graduate student mainly in the electric power systemResearch, design, production, experiment, construction, management, education etc. unit employment, be engaged in establishing of electric power system, power plant and related industrial realm electrical engineering to account, circulate, install, Adjust to try, research teaching, technique development, technocracy etc. unit employment.The electrical engineering and its automation profession introducesThe antenna of electrical engineering and its automation stretches toward every trade, small greatly arrive the research of astronautics airplane to the design of a switch, all have its figure. The professional student canBe engaged in electrical engineering- related system to circulate, the automatic control, electric power electronics technique, information handle, experiment technique, develop development, economy management and electronics and calculator techniqueApply the work of waiting the realm, is the breadth caliber"compound type" deluxe engineering technique talented person.The need of realm to level talented person of Gao is very big.According to the estimate, get into along with the foreign big business enterprise, Will appear very big indentation in this professional realm, may appear the phenomenon of talented person's supply falls short of demand very much at that time.A, profession synthesize to introduce electrical engineering and it automation the profession is electricity letterA newly arisen academics of interest realm, but because of with people's daily life with and industry produce closely related, develop very quickly, also opposite more mature now.Have already become Gao XinThe importance of the technique industry constitutes part, extensively is applied to realms, such as industry, agriculture and national defense...etc., develop a more and more important function in the national economy. Control a theory and electric power net reasonThe theory is an electrical engineering and automates professional foundation, the electric power electronics technique, calculator technique is also then its main technique means, included system analysis, system design and system at the same timeDevelopment and system management and decision etc. grind to investigate realm. Theprofession has some a characteristics, is a strong or weak electricity to combine, the electrician's electronics technique combine together, software and hardware combine together,Have the property that cross the academics, electric power, electronics, control, calculator many academics comprehensive, make the graduate student have a stronger orientation ability the dint is "breadth caliber" profession. Two, the profession teachIt is reason, work and text to combine together to teach to develop condition electrical engineering and automation profession, melt mechanical engineering, Art and calculator Be designed to integral whole of new cross an academics profession of a.LordThe dry academics includes electronics engineering, calculator science and technology and control science and engineering. This is professional to produce in 70's, first at oxford university, the beginning is the control method of direct current, Carry out a driving of component at that time what electric voltage is a direct current, control electric voltage is also a direct current of, the work method of automation is easy, rough, the accuracy is also very low. But direct current ofControl a way because its history of long ago but be been familiar with by people, involuntary people thought of to control an exchanges performance component with the direct current.Along with transistor, big power transistor and fieldThe effect tube waits the emergence and maturity of the electronics spare part of big power and builds up presently and theoretically, with now Algebra, matrix algebra for the weak electricity of the theory basis the strong electricity control system to make moreElectronics technique and automation attain new history height.To this, this profession got the university of extensive development, Japan, the United States and England and other nations to also establish this profession in succession,Is also many in the achievement in this period, if complete a number to control tool machine, the car factory premises automatically controls of the work is already a new topic.Electronics technique and automation, calculator of organic combine, endow withTo the electronics engineering and the automation profession is with the all new content.Is unmanned to manipulate, system simplification, structure and form reasonable, the product of plug-and-play type becomes lately spoiling. Found a nation an early our country many universitiesEstablished this profession, mainly practice sex teaching link to include the electric circuit and electronics technique experiment, electronics craft practice, gold work practice course design, production practice, graduation design, and for the countryHouse develop many of the aspect person just.They have become the expert scholar of profession industry, in the our country many provinces, city, become framework strength. "Cultural Revolution" period, political because of being subjected toInfluence, the high etc. college of whole country stops soliciting students one after another, this profession was subjected to very bigOf influence can stop soliciting students.But, even if such, many teachers didn't stop a research.They know electronics engineering and from move to turn the modernization construction to the our country to rise importantFunction, as a result, they didn't give up to the professional research and quest. Reform after opening, under the leadership of party the center, the university instauration solicits students, this profession also develops, manyThe university established this profession, and continuously solicit students, annually for the country development in the house in great quantities deluxe compound type talented person, include high classes, such as bachelor's degree and Doctor...etc. to know to know member, especially currently, each particularlyThe industry expands to recruit, soliciting students of this profession quantity is also rising.Although the our country follows before the development of this aspect hasn't stood on the world most,the our country synthesizes the exaltation of national strength along with the our country and outward associateIncrease, we narrow gradually with the hair reach nation of margin.What to have a representative is:Each 300,000,000,000 calculators develop success;Na rice technical control;Imitate a technical application. But a problem that allows of no to neglect: How to greet the challenge of new technique revolution?After this professional experts of joint effort, expand the electronics engineering and the automation profession to open,Is divided into "electric power system and its automation" and"electronics information engineering", cover to originally possessed "insulate a technique" "the electricity insulates and electric cable""electrical engineering electric appliances and its control""electricity workDistance and it, , , automation""application electronics technique" is with a few professional directions like"light source and lighting",etcs.Establish "Gao electric voltage with insulate a technique", , "electrical engineering and electric appliances""Electric power electronics and electric power spread" and"electrician the theory is with new technique""Gao electric voltage with insulate a technique" Bo, , private academic degree bine take industrial product design as foundation, applyCalculator shape, design, carry out structure, sex of industrial product ability, process, the design of shape etc. with excellent turn.The professional development orientation is social urgent, current firm science technique radicleThe Chu has art innovation again the ability of deluxe compound type technique talented person.This profession emphasizes to train the application, product shape of the student's foreign language, calculator, design...etc. to physically work ability and carry out evenNoodles design, stereoscopic design etc. product designs of the overall intelligence turn.The professional graduate student can be engaged in industrial product shape design, calculator application, sense of vision to inform design and environment design, wideTell the teaching, research, production, development and management work that the creativity, business enterprise image plans etc. profession.Bagged electric circuit principle, electronics technique foundation, electrical engineering to learn, electric power electronics technique, The electric power drags along with control, calculator technique(language, software foundation, hardware foundation, list slice machine etc.), signal and system and control courses like theory,etc.Higher class still according to societyNeeding to be studied is gentle, strong adaptability, the professional lesson and professional free elective course of coverage breadth.Also carry on electrical engineering and control experiment, electronics engineering at the same time system experiment and electric power electronics experiment etc.. Always, the our country is in CIMS and automatically control, robot product, the appropriation integrated circuit etc. contained substantial progress.For example: "Turn according to the integration of tiny machine environmentCAPP applied frame and development platform"developed to take craft knowledge base as to check heart of, with hand over a type to design with each other mode for foundation of comprehensive the intelligence turn CAPP to develop platform and application frame (CAPPFramework), release series products, such as gold leaf CAPP and together square CAPP...etc..Have to support craft knowledge model and dynamic state knowledge to obtain, the design and information of each kind of craftManage, the product craft information share, support the characteristic radicle create into a craft decision etc. function, and provide craft knowledge database management, craft card format definition etc. application support tool with two times openDeliver tool.The system opens sex well, be easy to enlargement and Wei to protect.Product already the business enterprise in whole country, especially CIMS model engineering business enterprise, expansion applied, also develop automatic control deviceAnd series product, the red and outside optoelectronics type safe protection equips, the development of big power, high-quality switch the power.The robot product includes to move a Dragon gate type to automatically spray Tu Ji, dynamoelectric spray machineThe person is gentle to imitate a form to automatically spray Tu Ji, the back and forth type sprays Tu Ji, automatic Tu Jiao's robot, frame type robot, porterage robot, developing of the robot of Hu Han.Above these productses openThe hair application returns just electronics engineering and automation are in an on the side in the production, is not enough to reflect its entire content.The forerunner carries on lately a skill from each aspect under the technical impact abroadThe Shu reorganizes. Employment direction the professional direction has very nice development prospect, therefore under the environment of the disadvantageous employment of outside economic crisis my Yi however decidedly want to choose electricityEngineering and automation are professional.Electrical engineering and automation the profession study the achievement more easily produce an article conversion to the reality, and the efficiency is very considerable.Although employment and economic situation are rigorous, But also be full of opportunity.The our country also really needs the professional talented person now, small all can not get away from these professional talented persons to a family, greatly to the whole society.Under the general circumstance,The student can choose stateowned quality technical director section, graduate school and work mineral business enterprise etc. after graduating;Can be some outsides property and private enterprise, the treatment is certainly considerable.Such asThe fruit ability is enough strong, again during the period of study backlog a little bit well grind to investigate an achievement, oneself completely can start a business and rush an one to belong to his/her own the sky.。

纳米技术在阿尔茨海默病药物治疗中的应用_机遇与挑战_高小玲

纳米技术在阿尔茨海默病药物治疗中的应用_机遇与挑战_高小玲

·专家论坛·纳米技术在阿尔茨海默病药物治疗中的应用:机遇与挑战高小玲,谷晓,陈红专(上海交通大学医学院基础医学院药理学教研室,上海200025)关键词:阿尔茨海默病;血脑屏障;纳米技术中图分类号:R749.16文献识别码:A文章编号:1673-6087(2015)02-0095-04DOI:10.16138/j.1673-6087.2015.02.006阿尔茨海默病(Alzheimer’s disease,AD)因最早由德国医师Alois Alzheimer发现而得名。

自1906年首例报道至今,AD已成为困扰人类最常见的痴呆疾病类型。

随着人口老龄化加剧,寻求延缓和治疗AD的有效方法变得越来越迫切。

目前治疗AD的药物开发主要面临两大困难:一是AD的发病机制尚未阐明,二是保护中枢神经系统的屏障结构阻碍了药物的脑内递送。

近十年来,纳米技术的发展给AD治疗药物的脑内递送带来了新的希望。

与传统给药方式相比,纳米递药策略有着独特优势:可提高药物的稳定性、靶向性以及血脑屏障(blood brain barrier)穿透性等。

因此,纳米递药策略在AD治疗领域极具应用前景。

本文将围绕纳米递药技术在AD治疗策略中的应用进行阐述,探讨其机遇与挑战。

阐明AD的发病机制仍是药物研发的关键瓶颈AD的主要病理特征为脑内的β淀粉样蛋白(amyloidβ,Aβ)沉积和神经细胞内的神经原纤维缠结,但目前研究尚未能揭示这些病理特征与其发病之间的因果关系,也不清楚AD发病的具体诱因。

现有AD治疗药物研发主要基于若干AD发病机制假说,但任何一个假说都不能独立解释AD的发病进程。

这也是目前AD治疗药物研发的关键瓶颈。

一、Aβ级联假说作为最受关注的AD病因假说,Aβ级联假说认为Aβ在AD发病进程中起关键作用[1]。

正常情况下,脑内Aβ的产生与清除保持平衡;而AD患者的这种平衡被打破,脑内Aβ聚集,进而引起其周边神经元突触功能障碍、τ蛋白过度磷酸化、氧化应激和继发炎性反应,导致神经元变性死亡,最终产生痴呆。

美军雷达命名规则和雷达英文词汇

美军雷达命名规则和雷达英文词汇

美军雷达命名规范按老美军用标准MIL-STD-196D规定,其军用电子设备(包括雷达)根据联合电子类型命名系统(JETDS)。

名称由字母AN(陆军-海军联合命名系统),一条斜线和另外三个字母组成。

三个字母表示设备安装位置,设备类型和设备用途。

比如AN/SPS-49表示舰载警戒雷达。

数字49标识特定装备,并且表示该设备时JETDS规定的SPS类的第49种。

经过一次修改就在原型后附加一个字母如ABC,名称后加破折号,T和数字表示丫是用来训练的。

名称后的括号内V表示丫是可变系统,就是通过增加或减少设备来完成不同功能的系统。

处于试验和研制中的系统有时在紧随正式名称后的括弧内用特殊标志来表示,他们用来指明研究单位。

比如XB表示海军研究实验室,XW表示罗姆航空发展中心。

下面就把AN/***后面的三个字母的意思祥加说明。

JETDS设备符号安装位置(第一个字母)A 机载B 水下移动式,潜艇D 无人驾驶运载工具F 地面固定G 地面通用K 水陆两用M 地面移动式P 便携式S 水面舰艇T 地面可运输式U 通用V 地面车载W 水面或水下Z 有人和无人驾驶空中运输工具设备类型(第二个字母)A 不可见光,热辐射设备C 载波设备D 放射性检测,指示,计算设备E 激光设备G 电报,电传设备I 内部通信和有线广播J 机电设备K 遥测设备L 电子对抗设备M 气象设备N 空中声测设备P 雷达Q 声纳和水声设备R 无线电设备S 专用设备,磁设备或组合设备T 电话(有线)设备V 目视和可见光设备W 武器特有设备X 传真和电视设备Y 数据处理设备设备用途(第三个字母)A 辅助装置B 轰炸C 通信(发射和接受)D 测向侦查或警戒E 弹射或投掷G 火控或探照灯瞄准H 记录K 计算M 维修或测试工具N 导航(测高,信标,罗盘,测深,进场)Q 专用或兼用R 接收,无源探测S 探测或测距,测向,搜索T 发射W 自动飞行或遥控X 识别Y 监视和火控有源滤波器Active filter有源校正网络Active corrective network有源干扰Active jamming机载引导雷达 Airborne director radar机载动目标显示 Airborne MTI机载雷达 Airborne radar机载截击雷达 Airborne-intercept radar机载警戒雷达 Airborne warning radar模拟信号 Analog signal天线抗干扰技术 Antenna anti-jamming technique天线增益 Antenna gain反辐射导弹 Anti-radiation missile背射天线 Backfire antenna回差 Backlash 轰炸雷达 Bombing radar平衡电感 Balancing inductor选频放大器 Bandpass amplifier战场侦察雷达 Battle-field search radar 盲区 Blind zone闪烁干扰 Blinking jamming击穿功率 Breakdown power体效应二极管本地振荡器 Bulk effect diode local oscillator宽带中频放大器 Broad band intermediate frequency amplifier机柜、分机结构 Cabinet, subassembly标定误差 Calibrated error电子束管(阴极射线管) Cathode-ray tube(CRT)空腔型振荡器 Cavity Oscillator谐振腔 Cavity Resonator空腔稳频本地振荡器 Cavity-Stabilized Local Oscillator干扰偶极子 Chaff Dipole信道化接收机 Channelized receiver圆极化平面波 Circularly polarized plane wave闭环控制系统(反馈控制系统)Close-loop control system (feed-back control system)杂波抑制 Clutter suppression同轴电缆 Coaxial cable 同轴谐振腔 Coaxial cavity同轴定向耦合器 Coaxial directional coupler 同轴滤波器 Coaxial filter相干振荡器 Coherent oscillator 相干动目标显示 Coherent MTI复调制干扰 Complex modulated jamming圆锥扫描雷达 Conical scan radar圆锥扫描天线 Conical Scanned Antenna连续波雷达接收机 Continuous-wave radar receiver对比度 Contrast 卷积器 Convolutor变频损耗 Conversion loss 相关时间 Correlation time抗反辐射导弹措施 Counter anti-radiation missile measures正交场器件(M型器件) Crossed-field devices(M-type devices)截止式衰减器 Cut-Off Attenutor截止波长 Cut-off wavelength连续波雷达发射机 CW Radar Transmitter直流阻抗 D.C. impedance直流谐振充电 D.C. resonant charging 直流谐振二极管充电 D.C. resonant diode charge数据处理 Data processing偏转线圈 Deflection coil延时充电电路 Delayed charging circuit介质移相器 Dielectric phase shifter介质干扰杆 Dielectric chaff rod数字滤波器 Digital filter数字匹配滤波器 Digital matched filter数字测距 Digital ranging引导雷达 Director radar多普勒雷达 Doppler Radar双门限检测器 Double threshold detector 双T接头 Double T-junction等效负载 Dummy load 天线收发开关 DuplexerE面(H面)折叠双T E plane (H plane) magic-T天线的有效面积 Effective area of an antenna有效辐射功率 Effective radiation power(E.R.P.)电液伺服阀 Electro-hydraulic Servo value电磁兼容性 Electromagnetic compatibility电子抗干扰 Electronic anti-jamming电扫描天线 Electronic Scanned antenna电扫描雷达 Electronically Scanned Radar椭圆极化场矢量 Elliptically Polarized Field Vector末制导雷达 End-guidance radar激励器(预调器、触发器) Exciter(premodulator, trigger)极窄脉冲雷达 Extra-short pulse radar快速付里叶变换 Fast Fourier Transform馈电网络 Feed network 相控阵馈电网络 Feed networks For Phased Array 铁氧体移相器 Ferrite phase shifter火控雷达 Fire control radar 频率捷变雷达 Frequency agile radar调频雷达发射机 Frequency modulation radar transmitter引信干扰 Fuse jamming齿轮传动误差 Gear transmission error图形失真校正 Graphic distortion correction格雷戈伦天线 Gregarain antenna制导雷达 Guidance radar炮瞄雷达 Gun directing radar 回旋管 Gyrotron测高雷达 Height-finding radar水平极化场矢量 Horizontally polarized field vector喇叭天线 Horn antenna 环行电桥 Hybrid ring液压泵 Hydraulic pump阻抗匹配 Impedance match 天线阻抗匹配 Impedance match of antenna输入阻抗 Input impedance 天线罩插入相移 Insertion phase of a radome阵列单元的孤立阻抗 Isolated impedance of an array element天线间的隔离 Isolation between antennas干扰压制系数 Jamming blanket factor干扰调制样式 Jamming modulation type干扰信号带宽 Jamming signal band width速调管 Klystron激光雷达Laser radar 线阵天线Linear array antenna 负载阻抗Load impedance低空搜索雷达 Low altitude surveillance radar主振放大式发射机 M.O.P.A. transmitter磁脉冲调制器 Magnetic pulse modulator 磁控管 Magnetron磁控管灯丝电压控制电路 Magnetron filament voltage controlling Circuit主瓣零点宽度 Main (major) lobe zero beamwidth航海雷达 Marine radar 矩阵阵列 Matrix array 气象雷达Meteorological radar微波带通滤波器 Microwave band-pass filter微波场效应晶体管放大器 Microwave field effect transistor amplifier微波全息雷达 Microwave hologram radar微波低通滤波器 Microwave low-pass filter副瓣电平 Minor (side) lobe level机动雷达Movable radar 阵列天线的互耦Mutual coupling of an arrayantenna多模馈电器 Multimode feed 多基地雷达 Multistatic radar多端网络 Multiport network导航雷达 Navigation radar 噪声调幅干扰 Noise AM jamming噪声调幅调相干扰 Noise AM-PM jamming归一化差斜率 Normalized difference slope单通道单脉冲雷达 One-channel Monopulse Radar开环系统频率特性 Open-loop system frequency characteristic运算放大器 Operational Amplifier超视距雷达 Over-the-horizon radar过压保护电路 Overvoltage protection circuit抛物柱面天线 Parabolic cylindrical antenna参量检测器 Parameter detector无源雷达 Passive radar相位检波器 Phase detector 移相器 Phase detector相控阵天线 Phased array antenna 锁相接收机 Phase-locked receiver相位扫描雷达 Phase-scanned radar脉冲压缩雷达Pulse compression radar 脉冲雷达接收机Pulse radar receiver相控阵的量化误差 Quantization error of a phased array雷达精度 Radar accuracy 雷达反侦察 Radar anti-reconnaissance天线罩 Radome采样频率 Sampling frequency 舰载雷达 Shipbased radar船用雷达 Shipboard radar 侧视雷达 Side-looking radar旁瓣对消 Sidelobe Cancellation固体微波振荡器 Solid state microwave oscillator合成孔径雷达 Synthetic radar目标识别雷达 Target-identification radar三通道单脉冲雷达接收机 Three-channel monopulse radar receiverT型(Y型)环行器(结环行器)T-type (Y-type) circulator (junction circulator)静电控制超高频电子管(栅控管) UHF electronstatic control tubeV形波束雷达 V-beam radar压控晶体振荡器 Voltage controlled oscillator波导谐振腔 Waveguide cavity天气雷达 Weather radar X-Y型天线座 X-Y type antenna pedestal八木天线 Yagi antenna雷达覆盖范围 Zone of radar coverage零轴漂移 Zero-axsis drift雷达工作模式:目标捕获系统:The tention action system(该系统配备有嵌入式惯性导航系统和全球定位系统,可在雷达快速展开时提供雷达位置坐标。

仑卡奈单抗在早期阿尔兹海默病治疗中的研究进展

仑卡奈单抗在早期阿尔兹海默病治疗中的研究进展

◇综述与讲座◇摘要仑卡奈单抗(lecanemab )是一种用于治疗伴有轻度认知功能障碍或轻度痴呆早期阿尔茨海默病(AD )的新药。

它是一种人源性抗A β原纤维的单克隆IgG1抗体,通过静脉注射进入患者体内,透过血脑屏障进入大脑,清除淀粉样蛋白斑块,使患者认知功能下降速度减慢,延缓疾病进展。

本文从仑卡奈单抗的药理研究、临床研究、安全性及局限性等方面进行综述,以帮助临床全面了解该药物的研究现状和已有成果。

关键词仑卡奈单抗;阿尔兹海默病;淀粉样蛋白β;临床研究;安全性中图分类号:R749.1文献标志码:A文章编号:1009-2501(2024)02-0207-08doi :10.12092/j.issn.1009-2501.2024.02.011阿尔茨海默病(Alzheimer's disease ,AD )是一种不可逆转的进行性神经退行性疾病,会影响患者的语言、记忆和思维能力以及日常活动[1]。

其主要病理特征包括淀粉样蛋白β(A β)斑块沉积和过度磷酸化的tau 蛋白形成的神经原纤维缠结[2]。

可溶性和不溶性聚集性A β的积累可能启动或加强AD 的病理过程[3]。

到目前为止,只有少数获批的治疗AD 的药物在临床上应用,但这些药物的效果仅限于AD 部分症状缓解,无法改变疾病进展[2]。

2023年1月6日,仑卡奈单抗(lecanemab ,商品名LEQEMBI )在美国获得首次批准用于治疗AD ,于2022年12月22日在我国申报上市。

仑卡奈单抗是一种人源化单克隆免疫球蛋白G1(IgG1)抗体,与可溶性淀粉样蛋白β(A β)原纤维高亲和力结合,可减少脑中A β斑块并预防其形成,从而延缓AD 的进展[3]。

在开始使用仑卡奈单抗之前,应确认A β病理的存在,在轻度认知障碍或轻度痴呆症阶段的患者中开始治疗[1]。

本文即对仑卡奈单抗的作用机制、药理研究、临床研究、安全性及局限性等进行综述。

1仑卡奈单抗的基本介绍1.1作用机制仑卡奈单抗是一种重组人源化免疫球蛋γ1(IgG1)单克隆抗体,优先靶向可溶性聚集的A β,对不溶性原纤维也具有活性[4]。

细说移动通信中的新技术(A new technology in mobile communicati

细说移动通信中的新技术(A new technology in mobile communicati

细说移动通信中的新技术(A new technology in mobilecommunication)As people's living space, activity space and participation areas continue to expand, the functional requirements of mobile phones, not only dialogue and communication, there are many other functions. Moreover, the existing communication system there exist many unsatisfactory places, such as system capacity, voice distortion, dropped on line, power radiation and slow data transmission, the existing communication technology alone is not enough to meet the new demands of communication people. So in this case, we must have new communication technology to ensure, so that a variety of emerging communication technology came into being, below is some of the 3G communications may be used in the new technology.1. Channel coding and decoding technologyThis technique may be used in the DS-CDMA communication standard, in which channel coding and decoding is mainly to reduce the signal transmission power and solve the inevitable fading problem of the signal in the wireless communication environment. The use of codec technology combined with interleaving can improve the BER performance, compared with no encoding, convolutional codes can improve the bit error rate is two orders of magnitude reached 10-3~10-4, and the DS-CDMA communication system using Turbo code error rate can be increased to 10-6. DS-CDMA candidate channel coding techniques include Reed-Solomon and Turbo codes, and Turbo codes can be used as 3G data encoding and decoding technology because the encoding and decoding performance can approach the Shannonlimit. Convolutional codes are mainly used for low data rate speech and signaling.2. Smart antenna technologyIn the development of mobile communication technology, smart antenna has become one of the most active fields. In recent years, almost all advanced mobile communication systems will use this technology. The advantage of smart antenna technology to mobile communication system is difficult to replace by any technology at present. Smart antenna technology has become one of the most attractive technologies in mobile communications. Smart antenna technology uses adaptive beamforming technology to improve the user's direction of arrival gain, while using the zero of the pattern to reduce the interference of high-power users on the space. Its main difficulties lie in the inconsistency of multi-channel and correction technology, the complexity of RAKE receiver combining baseband processing, and the inconsistency of the uplink and downlink direction of arrival caused by FDD technology.3, multi user detection technologyIn the third generation mobile communication system, WCDMA system is a typical example of application of multi user detection technology. As one of the key technologies in WCDMA system, multi user detection technology can make the system achieve good performance in high speed channel environment. Multiuser detection technology improves system performance and increases system capacity by removing cell interference. Multiuser detection technology can effectively mitigate thefar / near effects in DSSS WCDMA systems. The difficulty is the high complexity of baseband processing.4 、 soft handover technologyThe largest mobile phone users opinions on the network is often lost, now people not only during the call by its bitter, but some people worry that if the future network fax support, will not be dropped due to the problems of wireless fax into the water". This is because the mobile phone is switched more when the "hard switching", from a base station coverage area into another base station coverage area to break the original base station and the base station to contact, and then look for new entrants into the coverage area, which is commonly referred to as "first off", of course the off time difference of only a few hundred milliseconds, under normal circumstances, people can not feel, but once the mobile phone for entering the shield area or channel busy and unable to contact with a new base station, it will fall; CDMA technology is used in "soft switching", in the handover, mobile phone and continue to fall and the original base station the contact and contact with the new base station when the mobile phone has been confirmed and the new base station, the original base station and the link is broken, "and then off, dropping may be almost nothing.5, PHS TechnologyThe English name of PHS is Personal Handyphone System,Chinese meaning is personal mobile phone system, the network system is developed by the Japan Telegraph Company, it usesdigital transmission mode, combined with advanced radio access technology and intelligent digital network capabilities. PHS uses low power to transmit radio wave signals, so it covers a smaller area and is more suitable for urban areas, and relatively low rates. PHS provides complete communications services, the integrity of the data transmission ability to support wireless multimedia communication, secondly, PHS also offers a variety of Internet interface, such as: radio access, telephone lines, fiber optic cable, and because of its base design is very light, can support such as KTV. Street。

射频微波工程百科全书_toc

射频微波工程百科全书_toc

CUSIIC ContentsPreface (v)Contributors (vii)A/D and D/A Conversion Architectures and Techniques to Attenuators (1)A/D and D/A Conversion Architectures and Techniques (1)Acoustic Microwave Devices (24)Active Antennas (34)Active Filters: Overview of Active-filter Structures (56)Active Filters: Tools and Techniques for Active-filter Design (70)Adaptive Array Antennas (88)Altimeters (103)Amplitude Shift Keying (117)Analytical and Adaptive Modeling of Nonlinear High-power Amplifiers (127)Anisotropy and Bianisotropy (137)Antenna Accessories (147)Antenna Anechoic Chambers (158)Antenna Arrays for Mobile Communications (164)Antenna Compact Range (177)Antenna Feeds (185)Antenna Parameters (217)Antenna Radiation Patterns (225)Antenna Reverberation Chamber (239)Antenna Scanning Arrays (251)Antenna Testing and Measurements (262)Antenna Theory (269)Antennas (284)Antennas for High-frequency Broadcasting (295)Antennas for Medium-frequency Broadcasting (301)Antennas for Mobile Communications (319)Aperture Antennas (365)Application of Wavelets to Electromagnetic Problems (377)xviii ContentsApplied Numerical Electromagnetic Analysis for Planar High-frequency Circuits (397)Artificial Magnetic Conductor (413)Attenuation Measurement (434)Attenuators (452)Backscatter to Buried Object Detection (481)Backscatter (481)Bandpass Filters (494)Bandstop Filters (498)BiCMOS Devices and RF Integrated Circuits (499)Biological Effects of Radiofrequency Energy as Related to Health and Safety (511)Boundary-value Problems (523)Buried Object Detection (540)Calibration of a Circular Loop Antenna to Cryogenic Electronics (560)Calibration of a Circular Loop Antenna (560)Capacitance Extraction (565)Cavity Resonators (576)Cellular Radio (592)Chebyshev Filters (600)Chirality (610)Circuit Stability (622)Circuit Tuning (632)Circular Waveguides (643)Coaxial Line Discontinuities (653)Coaxial Lines and Waveguides (658)Combline Filters (674)Complex Media (694)Computational Electromagnetic Scattering Models for Microwave Remote Sensing (718)Conformal Antennas (750)Conformal Mapping Techniques (760)Conical Antennas (775)Coplanar Stripline (CPS) Components (780)Coplanar Stripline Transitions (810)Coplanar Waveguide Components (816)Coplanar Waveguide (CPW) Transmission Lines (821)Corrugated Horn Antennas (833)Coulomb Gauge in Electromagnetics, the (849)Coupled Transmission Lines (863)Cryogenic Electronics (882)Contents xix Dielectric Loaded Antennas to Dual- and Multi-frequency Microstrip Antennas (893)Dielectric Loaded Antennas (893)Dielectric Measurement (916)Dielectric Permittivity and Loss (938)Dielectric Resonator Antennas (960)Dielectric Resonator Filters (974)Dielectric Resonator Oscillators (985)Dielectric Resonators (999)Digital Microwave Receivers (1014)Digital Radio (1021)Diodes (1033)Dipole Antennas and Arrays (1046)Direct Satellite Television Broadcasting (1052)Direction of Arrival Estimation and Adaptive Processing Using a Conformal Phased Array (1065)Directional Couplers (1076)Directive Antennas (1085)Distributed Amplifiers (1086)Dual- and Multi-frequency Microstrip Antennas (1098)Electromagnetic-bandgap-assisted Bandpass Filters to Enhancements of the Finite Difference Time Domain Method (1117)Electromagnetic-bandgap-assisted Bandpass Filters (1117)Electromagnetic Compatibility (1136)Electromagnetic Ferrite Tile Absorber (1151)Electromagnetic Field Computation in Planar Multilayers (1163)Electromagnetic Field Measurement (1190)Electromagnetic Inverse Problems (1200)Electromagnetic Materials (1216)Electromagnetic Modeling (1232)Electromagnetic Shielding (1248)Electromagnetic Subsurface Remote Sensing (1256)Electromagnetic Surface Waves (1270)Electromagnetic Wave Propagation (1280)Electromagnetic Wave Scattering (1295)Electromagnetic Waves in Ionosphere (1303)Electromagnetics, Time-domain (1318)Electronic Warfare (1333)Elliptic Filters (1353)Enhancements of the Finite Difference Time Domain Method (1361)xx ContentsFabry-Perot Resonators to Friis Free-space Transmission Formula (1381)Fabry-Perot Resonators (1381)Fast Fourier Transforms and NUFFT (1401)Feedback Amplifiers (1418)Feedback Oscillators (1432)Feedforward Amplifiers (1439)Ferrite Circulators (1448)Ferrite Isolators (1473)Ferrite-loaded Waveguides (1486)Ferrite Phase Shifters (1497)Ferroelectric Materials (1504)Filter Synthesis (1521)Filter Theory (1548)Finite-difference Time-domain Analysis (1567)Finite Element Analysis (1589)Finline Components (1601)Finlines (1609)Fractal-shaped Antennas: a Review (1620)Frequency Converters and Mixers (1635)Frequency-division Multiplexers (1649)Frequency-domain Circuit Analysis (1659)Frequency-independent Antennas (1674)Frequency Modulation (1691)Frequency Selective Surfaces (1700)Frequency Stability (1706)Frequency Standards, Characterization (1720)Frequency Synthesizers (1729)Friis Free-space Transmission Formula (1733)Galerkin Method (Rayleigh-Ritz Method) to Gyrotrons (1735)Galerkin Method (Rayleigh-Ritz Method) (1735)Gallium Arsenide Technology and Applications (1749)Gallium Nitride for Electronics (1758)Generalized Scattering Matrix Technique (1767)Geometrical Optics (1777)Ge-Si Alloys and Devices (1796)Gratings, Grating Antennas (1806)Green’s Function Methods (1817)Ground Penetrating Radar (1833)Contents xxiGuided Electromagnetic Waves (1846)Gunn or Transferred-electron Devices and Circuits (1857)Gyrators (1874)Gyrotrons (1883)Hankel Transforms to Hybrids and Couplers (1893)Hankel Transforms (1893)Harmonic Oscillators, Circuits (1915)Helical Antennas (1925)Helmholtz Equations (1936)Heterojunction Bipolar Transistor (1946)Heterostructures Devices (1963)High-field Effects (1970)High-frequency Broadcasting (1981)High-frequency Transmission Lines (1989)High-temperature Superconductors (2005)History of Wireless Communication (2015)Horn Antennas (2021)HTS Film Growth (2032)Hybrid CAD Techniques (2040)Hybrids and Couplers (2054)IMPATT Diodes and Circuits to ITS Radio Service Standards and Wireless Access in Vehicular Environments (ITS-WAVE) at 5.9 GHz (2067)IMPATT Diodes and Circuits (2067)Impedance Transformers and Matching Networks (2079)Indium Phosphide (InP) (2092)Integral Equations (2103)Integrated Antenna Systems (2113)Integrated Circuits (2147)Integro-differential Equations (2166)Intermediate-frequency Amplifiers (2175)Intermodulation (2189)Intermodulation Measurement (2215)Iterative Methods (2231)ITS Radio Service Standards and Wireless Access in Vehicular Environments (ITS-WAVE) at 5.9 GHz (2241)Klystron (2257)Klystron (2257)xxii ContentsLeaky Modes and High-frequency Effects in Microwave Integrated Circuits to Low-temperature Cofired Ceramic (LTCC) Technology in RF and MicrowaveEngineering (2268)Leaky Modes and High-frequency Effects in Microwave Integrated Circuits (2268)Leaky-wave Antennas (2294)Left-handed Materials for Microwave Devices and Circuits (2303)Lens Antennas (2320)Linear Antennas (2336)Local-area Networks (LANs) (2352)Loop Antennas (2359)Low Noise Amplifiers (2368)Low Noise Amplifiers: Device Noise Characterization and Design (2379)Low-pass Filters (2383)Low-power Broadcasting (2385)Low-temperature Cofired Ceramic (LTCC) Technology in RF and Microwave Engineering (2393)Magnetic Field Measurement to Multiresolution Technique (2400)Magnetic Field Measurement (2400)Magnetic Materials (2412)Magnetic Microwave Devices (2425)Magnetic Resonance Imaging (2462)Magnetic Shielding (2473)Magnetrons (2482)Maxwellian Circuits (2514)Measurement of Near Fields Using a Modulated Scatterer (2522)Medical Imaging with Microwave: Thermoacoustic Tomography (2530)MEI Method (2540)Method of Lines (2548)Method of Moments (2554)Microstrip Antenna Arrays (2568)Microstrip Antennas (2580)Microstrip Antennas, Broadband (2602)Microstrip Antennas, Compact (2626)Microstrip Circuits (2637)Microstrip Lines (2647)Microstrip Transitions (2654)Microwave and Radio Frequency Multipliers (2663)Microwave Circuits (2704)Microwave Detectors (2736)Microwave Filters (2751)Contents xxiiiMicrowave Heating (2763)Microwave Integrated Circuits (2773)Microwave Isolators (2786)Microwave Limiters (2792)Microwave Measurements (2802)Microwave Mixers (2812)Microwave Oscillators (2818)Microwave Parametric Amplifiers (2827)Microwave Phase Shifters (2836)Microwave Photonics: Technological Evolution and Its Applications (2851)Microwave Power Amplifiers (2871)Microwave Power Transmission (2906)Microwave Receivers (2919)Microwave Resonance Plasma Source (2934)Microwave Scattering Models for Earth Terrain (2948)Microwave Solid-state Devices (2968)Microwave Superconductor Devices (2980)Microwave Switches (2991)Microwave Tubes (2999)Military Communication (3007)Millimeter-wave Integrated Circuits (3021)Millimeter-wave Measurement (3046)MIMO Systems for Wireless Communications (3059)Miniaturized Packaged (Embedded) Antennas for Portable Wireless Devices (3068)Missile Guidance (3082)Mixed-signal CMOS RF Integrated Circuits (3095)Mixer Circuits (3102)Mobile Communication (3121)Mobile Radio Channels (3132)Mobile Satellite Communications (3150)Mode-matching Methods (3162)Modulation-doped FETs (3176)Monolithic Antennas (3203)Monolithic Microwave Integrated Circuits (MMICs) (3213)Monopole Antennas (3238)Monopulse Tracking Systems (3244)Monte Carlo Analysis (3255)Monte Carlo Simulation in Reliability (3269)Mosfet Modeling (3278)xxiv ContentsMultibeam Antennas (3317)Multiconductor Transmission Lines (3335)Multimode Equivalent Network Representations (3342)Multiple Access Schemes (3351)Multiplexers (3362)Multiresolution Technique (3369)Negative Resistance to Notch Antennas (3385)Negative Resistance (3385)Neural Networks for Microwave Circuits (3390)Noise and Interference Modeling (3397)Noise Generators (3408)Noise, High-frequency (3417)Noise, Hot Carrier Effects (3439)Noise, Low-frequency (3458)Nonlinear Circuit Analysis (3482)Nonlinear Circuit Design (3502)Notch Antennas (3534)Orthomode Transducers to Oscillator Design (3547)Orthomode Transducers (3547)Oscillator Design (3563)Packaging RF Devices and Modules to Pulse-shaping Circuits (3590)Packaging RF Devices and Modules (3590)Parallel Algorithms and Computing for Large-scale Electromagnetic Simulation (3614)Parameter Estimation from Electromagnetic Simulations Using Signal Models (3646)Passivation (3669)Periodic Structures (3675)Permittivity and Measurements (3693)Personal Area Networking with Bluetooth (3711)Perturbation Theory (3725)Phase Locked Loops (3735)Phase Locked Oscillators and Frequency Synthesizers (3767)Phase Noise and Measurements (3802)Phase Shifters (3810)Photonic Band Gap (PGB) (3823)Piezoelectric Transducer Controlled Circuits (3838)Piezoelectricity (3846)Pin Diodes (3858)Contents xxvPower Combiners and Dividers (3869)Preamplifiers (3891)Printed Inductors (3905)Pulse Compression (3915)Pulse-shaping Circuits (3925)Q-factor to Quasi-optical Circuits (3937)Q-factor (3937)Q-factor Measurements (3948)Quadrature Phase Shift Keying (QPSK) (3964)Quasi-optical Circuits (3977)Radar Altimetry to Rough-surface Scattering: Numerical Simulations andApplications in Microwave Remote Sensing (3989)Radar Altimetry (3989)Radar Antennas (4005)Radar Applications (4018)Radar Cross-section (4030)Radar Equipment (4055)Radar Imaging (4069)Radar Polarimetry (4080)Radar Remote Sensing (4096)Radar Remote Sensing of Irregular Stratified Layers (4122)Radar Signal Detection (4128)Radar Signal Processing (4148)Radar Target Recognition (4165)Radar Tracking (4173)Radiation Effects (4186)Radiation Monitoring (4217)Radio Broadcast Studio Equipment (4227)Radio Direction Finding (4249)Radio-frequency Identification Systems (RFID) (4263)Radio-frequency Integrated Circuits (4269)Radio Navigation (4292)Radio Noise (4297)Radio on Fiber Systems (RoF Systems) (4310)Radio Reception (4324)Radiometry (4342)Radiotelemetry (4350)Radiowave Propagation Concepts (4365)xxvi ContentsRadiowave Propagation Ground Effects (4371)Radiowave Propagation in Multipath Channels (4389)Reconfigurable Antennas (4405)Rectifying Antennas (Rectennas) (4418)Reflectarray Antenna (4428)Reflectometers, Time-domain (4436)Reflector Antennas (Parabolic Antenas, Dish Antenas) (4450)Refraction and Attenuation in Troposphere (4475)Resonant Tunneling Diodes (4484)Retrodirective Systems (4493)RF Circuit Noise (4507)RF/Wireless Packaging (4516)Ring Resonators and Circuits (4537)Rough-surface Scattering: Numerical Simulations and Applications in Microwave RemoteSensing (4549)Satellite Antennas to Synthetic Aperture Radar (4585)Satellite Antennas (4585)Schottky Barrier Diodes and Their Applications (4595)Schottky Barriers (4607)SiC Device Technologies (4613)Signal Fading in Radiocommunications (4619)Silicon-Germanium (4626)Six-port Networks (4641)Skin Effect (4669)Sky Wave Propagation at Low Frequencies (4675)Sky Wave Propagation at Medium and High Frequencies (4686)Slot Antennas (4696)Slotline Components (4717)Slotlines (4736)Slow Wave Structures (4744)Small Antennas (4761)Smart Materials (4799)Smith Chart (4814)Spaceborne Radar (4823)Spatial and Quasi-optical Power Combining (4837)Spice (4844)Spiral Antennas (4853)Squids (4869)Stability of Nonlinear Systems (4881)Contents xxviiStanding Wave Meters and Network Analyzers (4896)Strip Transmission Lines (4918)Stripline Components (4931)Submarine Antennas (4937)Superconducting Cavity Resonators (4951)Superconducting Electromagnets (4965)Superconducting Filters and Passive Components (4974)Superconducting Microwave Technology (4990)Surface Acoustic Wave Applications (5002)Surface Acoustic Wave Delay Lines (5012)Surface Acoustic Wave Devices (5029)Surface Acoustic Wave Filters (5046)Surface Mount Technology (5058)Synthetic Aperture Radar (5067)Target Tracking to Tunnel Devices (5081)Target Tracking (5081)Telemedicine (5097)Telemetry (5106)Television and FM Broadcasting Antennas (5124)Television Antennas (5132)Television Broadcast Transmission Standards (5143)Terahertz Science, Engineering and Systems – from Space to Earth Applications (5175)Thermal Analysis and Design of Electronic Systems (5194)Thin Film Resistors (5213)Thin Films (5226)III-V Semiconductors (5237)Transceivers (5254)Transient Analysis (5268)Transmission Line Matrix (TLM) Method (5286)Transmission Line Theory (5297)Transmission Lines and Parameters (5310)Transmitters for Analog Television (5318)Transmitters for Digital Television (5327)Transmitters for FM Broadcasting (5337)Transverse Resonance Techniques (5357)Traveling Wave Antennas (5363)Traveling Wave Tubes (5373)Tunnel Devices (5380)xxviii ContentsUHF Receivers to Uniform Geometrical Theory of Diffraction (5391)UHF Receivers (5391)Ultra-wideband Radio (5402)Ultra-wideband Wireless Systems (5411)Underground Propagation (5423)Uniform Geometrical Theory of Diffraction (5433)Van Atta Array Reflector to Volterra Modeling in Analog, RF and MicrowaveEngineering (5456)Van Atta Array Reflector (5456)Variable-frequency Oscillators (5468)Very High Frequency Range (5477)Voltage-to-frequency Converters (5489)Volterra Modeling in Analog, RF and Microwave Engineering (5507)Waveguide Antennas to Wireless Communications Systems (5515)Waveguide Antennas (5515)Waveguide Components (5527)Waveguide Directional Couplers (5536)Waveguide Discontinuities (5543)Waveguide Junctions (5554)Waveguide Oscillators (5559)Waveguides (5569)Wavelength Meter (5587)Wavelet Transforms (5602)Wavelets (5623)Wideband Amplifiers (5630)Wideband Slot and Printed Antennas (5638)Wireless Communications Systems (5656)Yagi-Uda Antenna (5680)Yagi-Uda Antenna (5680)Index (5691)。

Spotlight SAR data focusing based on a two-step processing approach

Spotlight SAR data focusing based on a two-step processing approach

Spotlight SAR Data Focusing Based on a Two-StepProcessing ApproachRiccardo Lanari,Senior Member,IEEE,Manlio Tesauro,Eugenio Sansosti,Member,IEEE,and Gianfranco FornaroAbstract—We present a new spotlight SAR data-focusing algo-rithm based on a two-step processing strategy that combines the advantages of two commonly adopted processing approaches:the efficiency of SPECAN algorithms and the precision of stripmap fo-cusing techniques.The first step of the proposed algorithm imple-ments a linear and space-invariant azimuth filtering that is carried out via a deramping-based technique representing a simplified ver-sion of the SPECAN approach.This operation allows us to perform a bulk azimuth raw data compression and to achieve a pixel spacing smaller than(or equal to)the expected azimuth resolution of the fully focused image.Thus,the azimuth spectral folding phenom-enon,typically affecting the spotlight data,is overcome,and the space-variant characteristics of the stripmap system transfer func-tion are preserved.Accordingly,the residual and precise focusing of the SAR data is achieved by applying a conventional stripmap processing procedure requiring a minor modification and imple-mented in the frequency domain.The extension of the proposed technique to the case of high bandwidth transmitted chirp signals is also discussed.Experiments carried out on real and simulated data confirm the validity of the presented approach,which is mainly focused on spaceborne systems.Index Terms—Raw data focusing,spectral analysis(SPECAN) processing algorithms.I.I NTRODUCTIONS YNTHETIC aperture radar(SAR)spotlight mode allows the generation of microwave images with high geometric resolutions[1],[2].This result is achieved by steering the radar antenna beam,during the raw data acquisition interval,to al-ways illuminate the same area on the ground(spot).Accord-ingly,from each target located in the lighted area,a large number of backscattered echoes is received,and their coherent combina-tion allows to obtain the required azimuth resolution.Similarly, high resolution in the range direction is achieved by transmitting a high bandwidth chirp followed by a further data processing on each received echo.The first algorithms proposed for spotlight raw data pro-cessing are based on the similarity between spotlight SAR systems and computer tomography:they are usually referredManuscript received March30,2000;revised November29,2000.This work was partially supported by the Italian Space Agency,Roma,Italy.The spotlight SIR-C data have been processed at the Jet Propulsion Laboratory,Pasadena,CA. nari,E.Sansosti,and G.Fornaro are with the Istituto di Ricerca per l’Elettromagnetismo e i Componenti Elettronici(IRECE)328I-80124 Napoli,Italy,(e-mail:lanari@r.it;sansosti@r.it; fornaro@r.it).M.Tesauro is with the Dipartimento di Ingegneria dell’Innovazione,Univer-sitàdegli Studi di Lecce,I-73100Lecce,Italy(e-mail:manlio.tesauro@unile.it). Publisher Item Identifier S0196-2892(01)07625-2.to as polar format and convolution backprojection techniques [3]–[5].The former are computationally efficient but request a nontrivial interpolation step from a polar to rectangular grid: the image quality can be therefore affected by uncompensated range curvature effects[6]and interpolation errors.The latter allow overcoming these limitations but are generally inefficient if implementations on dedicated architectures are not consid-ered[5].Most recently,the development of spotlight raw data processing algorithms based on stripmap mode focusing techniques operating in the frequency domain has received increasing interest[7]–[10].Indeed,strip-mode processing procedures that are precise,efficient,and requiring less stringent approximations(compared to those involved in the tomographic approaches)are available[11]–[13].However,a relevant limitation to the straightforward application of these techniques to the spotlight data processing is represented by the fact that the raw signal azimuth bandwidth is,in the spotlight case,generally greater(often much greater)than the azimuth sampling frequency,referred to as pulse repetition frequency(prf).As a consequence,data processing carried out in the Fourier domain,as that involved in efficient strip-mode focusing,cannot be directly implemented on the full aperture because of the consequential azimuth spectrum folding effect.A way to overcome this limitation is based on partitioning the received signal into azimuth blocks whose block-bandwidths are smaller than the sampling frequency.Standard strip mode focusing techniques are then applied to each data block and the processed signals are then combined to generate the fully-resolved spotlight image[9],[10].Completely different pro-cessing solutions,based on a nontrivial reconstruction of the unfolded azimuth spectrum from the folded one associated to the raw signal,are also available[7],[8].On the other hand,a relatively simple spotlight processing al-gorithm can be implemented by applying the spectral analysis (SPECAN)technique[14].In this case,the received raw data are azimuth focused via the application of a deramping func-tion(a multiplication by a properly chosen chirp signal)fol-lowed by a final azimuth FT operation.The azimuth deramping factor is updated in range to allow for the compensation of the space-varying characteristic of the received data due to the(az-imuth)chirp rate range variation(focus depth).This procedure is attractive as far as computational efficiency and capability to overcome the azimuth spectral folding effect are concerned. However,its main limitation is represented by the lack of a pre-cise range cell migration(RCM)compensation that is often rel-evant in spotlight mode SAR systems due to high resolution re-quirements.0196–2892/01$10.00©2001IEEEIn this paper,we propose an alternative spotlight data fo-cusing technique based on decoupling the overall focusing oper-ation in two main steps.The key point of the proposed approach is to combine the advantages of efficient SPECAN and precise stripmap focusing approaches.In particular,the first processing step carries out a filtering operation aimed to achieve a bulk az-imuth raw data compression and an output pixel spacing smaller than(or equal to)the expected final azimuth resolution.Similar to SPECAN processing algorithms,this filtering operation is ef-ficiently carried out via a deramping-based approach[14]but, at variance of the former,the chirp rate of the deramping func-tion is kept constant and properly fixed at a convenient value. This is a key point in the proposed processing procedure that al-lows preserving the space variant characteristic of the residual system transfer function(STF).A discussion on the impact of the chirp rate selection on possible artifacts that may appear at the image borders is also provided.The second processing step carries out the residual focusing of the data via the use of a conventional stripmap processing pro-cedure implemented in the frequency domain and requiring only minor modifications in the available codes.This spectral do-main focusing operation is now possible because,following the bulk azimuth compression,the folding effect of the raw signal azimuth spectrum has been totally overcome.More precisely, this second(residual)processing step performs the precise RCM compensation,the data range compression and the residual az-imuth data compression;the latter accounts for higher order terms not compensated in the bulk azimuth processing step.The minor modifications to be performed in available stripmap pro-cessing codes are essentially a change of the azimuth filter func-tion,which accounts for the already compensated quadratic az-imuth phase term,and a change in the azimuth pixel spacing of the input data.It is worth noting the role that the bulk azimuth compres-sion operation plays in our approach to a preprocessing step that extends the processing capability of conventional stripmap fo-cusing procedures to spotlight data.In addition,the proposed processing algorithm does not require a specific manipulation and/or interpolation of the data,such as those necessary in az-imuth block divisions or in unfolded signal spectrum reconstruc-tion-based algorithms.Accordingly,we have finally achieved a processing procedure that is simple,precise and computation-ally efficient because it does not imply any significant increase of the raw data matrix dimensions and only includes fast Fourier transforms(FFTs)and matrix multiplication.Moreover,it can be easily extended to the case of high bandwidth transmitted sig-nals wherein spectral folding effects could appear in the range direction as well.In our case,the implemented solution is based again on a deramping approach,that is,at variance of conven-tional focusing techniques performed following the A/D con-version rather than before.A number of experiments carried out on a simulated and a real data set,the latter acquired by the experimental C-band sensor of the SIR-C system during the SIR-C/X-SAR mission in1994[9],demonstrate the validity of the presented approach.As a final remark,we want to stress that the presented anal-ysis is focused on spaceborne systems typically characterized by small squint angles[15]during the acquisition(often lessthan Fig.1.Spotlight system geometry.1-axis,assumed coincident with the platform flight path,is referred to as azimuthdirection are the(closest approach)target range and look angle,respectively.1We assume in the following that the sensor,mounted onboard a platform moving at the constantvelocity,transmits,attimes(1) whereangular carrierfrequency;chirp rate,beingis the systemwavelength,,the two-way antenna pattern factor,and being the azimuth dimension of the real,onboard antenna.Note that the assumed simplificationon allows avoiding the antenna footprint dependence on the platform location whose impact is 1Note that we have assumed the platform trajectory to be a straight line which is appropriate for airborne but not for spaceborne sensors.However,it can be shown that spaceborne data can be processed in the same manner as airborne data if the closed approach distance and the azimuth velocity are properly con-sidered[16]or,more precisely,via the appropriate sensor-target distance eval-uation[17].LANARI et al.:SPOTLIGHT SAR DATA FOCUSING 1995inessential for the following analysis.A more detailed discus-sion on this matter can be found in [10].Let us now consider a pointtargetandreceived onboard is represented,after the heterodyne process [that removes the fast varyingterm(4a)FTis the azimuth (spatial)frequency.Equation (7)shows that theazimuth spectrum is centered on thefrequencyand that the signal bandwidthiswith respect to the strip mode case,for whichit wouldbe.In this case,weget(8)Since the maximum valueof,i.e.,that relative to the nearest range,should be con-sidered.This is assumed hereafter,although we underline that in the spotlight case,due to the typically limited range extension of the illuminated spot,the range dependenceof (9)in order to avoid any azimuth spectral folding effect [18].On the other hand,this sampling frequency increase would lead to large data rates and could generate severe range ambiguity problems [15].Accordingly,the valuesofand are the raw data and thefocused image azimuth pixel dimensions,respectively,the latter chosen in agreement with the Nyquist limit available from (8).In this case,we get from(9)(10)1996IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING,VOL.39,NO.9,SEPTEMBER2001 Equation(10)clarifies that the azimuth number of pixel inthe raw data set and in the focused image,i.e.,,respectively,are comparable,and they become closeras.III.B ULK A ZIMUTH R AW D ATA C OMPRESSIONLet us now investigate a possible solution to the azimuth spec-tral folding effect discussed in the previous section.The pro-posed approach is based on a linear and space-invariant azimuthfiltering operation that performs a bulk azimuth data compres-sion and achieves an output pixel spacing,satisfying the Nyquistlimit shown in(8).This operation is efficiently implementedwithout any large zero padding step,via a deramping-basedtechnique[1],[2],[14].A.Continuous Domain AnalysisKey point of the presented technique is the azimuth convolu-tion between the raw data and the quadratic phasesignal(11)whereinand are the nearest and the farthest ranges of theilluminated spot,respectively,and represents the range valueof a generic point target located within the spot.No specific as-sumption has yet been made on the factor in(11),althoughwe anticipate that the impact of any particular selection for thisterm is later discussed in detail.We also underline that the rawsignal range component,accounting for the range independent(RI)and range dependent(RD)RCM effects,is neglected inthe azimuth convolution operation presented in this section.Allthese components are restored and accounted for during the sub-sequent and highly precise second processing step.The azimuth convolution between thesignal in(5),forthe case of an isolated target,and thefunction in(11)gives(12)wherein thesymbolof the target and on the valueof.The second line in(12)shows that this azimuth convo-lution is essentially a deramping based(SPECAN)processing,involving a chirp multiplication of the azimuth signal,a subse-quent FT and a residual phase cancellation.Indeed,but for theabove mentioned approximations,this processing step allows usto achieve an azimuth compression which is full only for thosetargets locatedat.This point can be clarified by recon-sidering(12).Indeed,if weassume(13)wherein the imaged target is fully azimuth focused.Forany,by assuming the validity of theSPM method3weget,for which the resulting signal is centeredaround andextendsfor.However,because the range ex-tension of the spot area is typically very small,we canassumeand,even in this limiting case,a compression effect,althoughpartial with respect to that achieved in(13),is obtained.The obtained results apply to the case of an isolated target,however they can be easily extended to the case of an illumi-nated area.Accounting for the azimuth spotdimensionwith(16)3Generalization to those cases where SPM cannot be applied can be derivedas in[19].Here we are interested only in having a rough measure of the targetecho extension following the first processing step.LANARI et al.:SPOTLIGHT SAR DATA FOCUSING 1997with ,i.e.,with a pixel spacing satisfying the Nyquist limit of the spotlight signal,see (8)and (9).Accordingly,sim-ilarly to what is shown in the continuous analysis presented in the previous section,(12)becomesbeing the nearest integer operator.Note that,dueto(10),with (18)where thefactorrepresents the output azimuth data repli-cation.Accordingly,under the validity of the inequality in (18),not only the azimuth spectral folding effects are avoided,see (16),but also no data wrap around occurs in the azimuth direc-tion.We note that the validity of the aforementioned inequality in (18)is generally satisfied due to the presence of a slight az-imuth data oversampling carried out on the spotlight signal with respect to the Nyquist rate that we would have with the system operating in the stripmap mode.This point can be clarified by accounting for (15)in the inequality in (18).In this case,wegetgives a value ofaboutfor the right-hand side factor in (21).This leads tothe newinequality,which is satisfied for most real spotlight SAR systems.Of course in the (rare)case of an insufficient oversampling factor,a balancing choice would be represented by setting at the midrange swath,thus leading to a resolution degradation at the image near and far range edges.Anyway,we remark that this is generally not a very critical issue because,due to the antenna beam steering,those targets would be in any case characterized by a lower resolution [10].Based on (18),we can finally rewrite (17)asfollows:of the orderofis required and implemented via the substitu-tionin (11)[and equivalently in (17)]to compen-sate for this effect.Secondly,due to the appearance of a sig-nificant range walk effect [15]in the RCM,an additional edge degradation could appear even at midrange.Although the paper is focused on low squint angle acquisitions,we stress that well known procedures applied for mitigating the range walk effect in deramping-based focusing approaches could be considered [20].However,this is worth pursuing for future studies.4Notealso that,at variance with what is shown in (22),a more conventionalexpression of the DFT operation can be consideredimplying1with n =0P=2;...;P=201[18].Inthis case,a trivial manipulation of (22)is required.1998IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING,VOL.39,NO.9,SEPTEMBER2001 IV.R ESIDUAL D ATA F OCUSING VIA S TRIPMAPP ROCESSING T ECHNIQUESLet us concentrate on the result of the bulk azimuth com-pression step shown in(12).We underline that,following thisoperation,the folding effect influencing the azimuth spectrumis avoided and the space-variant characteristics of the systemtransfer function are maintained.Accordingly,it is possible tocarry out the residual focusing of the data via the use of effi-cient and precise techniques originally designed for stripmapSAR data focusing that are implemented in the frequency do-main.To clarify this point,we refer to the expression of the receivedsignal over a distributed scene by resorting the linearity of thesystemrepresents the reflectivity function of the illumi-nated scene including the fast varying phase term in(24).Thereceived data spectrum can be written asfollows:is the range(spatial)frequency,andcan be found via the application ofthe SPM,leading to the following expression[15]:(27)where,and.In this case,wehaveFT(29)wherein the phasefactor accounts for thebulk compression step.By finally substituting(27)in(29),weget(30)withinsteadof[15].Moreover,the folding effects influencing the azimuth raw signalspectrum(see Section II)have been avoided due to the alreadycarried out bulk azimuth compression step leading to the newpixelspacing shown in(18).We also note that the space-variant characteristics of the system transfer function are pre-served by the bulk compression.This nonlinear mapping of therange frequencies,i.e.,bysimply accounting for the system transfer functioncomponentinsteadof and by considering the new azimuth sam-pling frequency.In particular,we have considered the stripmap processing ap-proach described in[12],and the overall processing block dia-gram is shown in Fig.2.In this case,the first step carries out thebulk azimuth compression,while the residual focusing is im-plemented as follows:the filtering operation,carried out in thetwo-dimensional(2-D)frequency domain via the filterfunctionallows us to fully focus the midspot area by accountingLANARI et al.:SPOTLIGHT SAR DATA FOCUSING1999Fig. 2.Two-step focusing procedure block diagram.Note that i=0P=2;...;P=201and l=0M=2;...;M=201.Moreover,1=(P1x)and1=(M1ri i in i l i l inr r i l lo re i rara r l l i in i ir i ra r i i ira r i r i im l inis r i i la r in l ii r i l r if l id i x r ii r r ic l x r i re ii i2000IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING,VOL.39,NO.9,SEPTEMBER2001 Fig.4.C-band VV-polarized image of the Sidney zone obtained by applyingthe focusing approach of Fig.5to the raw data set acquired in1994by theSIR-C system operating in an experimental spotlight mode.The expectedazimuth resolution is about1m,but the image is represented with an azimuthpixel spacing of about6.5m to avoid the geometric distortions caused bydifferent dimensions of the pixel in range and azimuth directions.The extensionof the area is of about1.7km24.5km.range compressionof(zeropadded to increase its extensionfrom)and thesignalin(31),becomingLANARI et al.:SPOTLIGHT SAR DATA FOCUSING2001Fig.5.Simulated image obtained after the bulk azimuth compression(rangecompression has been also implemented).The range corresponding to~r ishighlighted.Clearly,although not explicitly mentioned,the range pixelspacing resulting from the range focusing operation of(33)must also be considered for the implementation of theresidual focusing step.As final remarks,we underline that all the operations involvedin(33)are assumed,in our case,to be carried out after the A/Dconversion in the receiver.Moreover,the computational effi-ciency of the procedure in Fig.3can be further improved bycombining the range compression operation and the compen-sation of the scaling factor2002IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING,VOL.39,NO.9,SEPTEMBER 2001TABLE IIR ESULTSOF THEA NALYSIS C ARRIED O UT ONTHE I MAGED P OINTT ARGETS OF F IG .61994by the C-band sensor of the SIR-C system operated in the experimental spotlight mode (see Table I for a description of the system parameters).In this case,because of theratiokm,andthe near,mid,and far range distancesarekm,km,and km,respectively.Theselected value ofiskm.Accordingly,based on the analysis of Section III,we can evaluate the minimum andmaximum range distance,forexampleand ,which ensure the absence of degradation at the edges of the image,by using (20).They are givenbyKmand(36)thus guaranteeing the possibility of focusing the overall scene.The image obtained by applying the procedure of Fig.2is pre-sented in Fig.4.It clearly shows the focusing capability of the proposed algorithm.However,the absence of known reference targets in the scene does not allow any significant quantitative measurement of the quality of the obtained image.Accordingly,in order to assess the performance of the proposed approach,we have generated a simulated data set representing the signal backscattered by a sequence of three point targets aligned in the range direction and located over an absorbing background.The system parameters are again those of Table I.To better clarify the effect of the bulk azimuth compression step,we show the result obtained by applying this operation (see Fig.5).As expected,the achieved azimuth compression 5effect is more relevant for the target located at a range closer to .We additionally remark that the azimuth extension of the bulk com-pressed data is of 2048samples,and it has been increased 6with respect to the raw data,by about 20%(the azimuth raw data length was of 1700samples),but no additional data dimension increase is required in the residual focusing step.Note also in5Inorder to improve the readability of the result,a range compression step has been also carried out.6This allowed the use of high efficient FFT codes with a power of two data lengths[18].Fig.7.High resolution simulated image obtained by applying the focusing procedure of Fig.3.The contour plots of the three imaged point targets are also shown.Fig.5the effect of the uncompensated range cell migration ef-fect.The fully focused image is finally shown in Fig.6.The results of the measurements carried out on the imaged point targets of Fig.6are summarized in Table II wherein the theoretical az-imuth resolution values are those pertinent to the selected point reflector.The inspection of Table II clarifies the high perfor-mance of the presented technique for what concerns the ampli-tude characteristics of the target responses.The phase accuracy has been also assessed;it is about 1LANARI et al.:SPOTLIGHT SAR DATA FOCUSING2003 TABLE IIIR ESULTS OF THE A NALYSIS C ARRIED O UT ON THE I MAGED P OINTT ARGETS OF F IG.712004IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING,VOL.39,NO.9,SEPTEMBER 2001different foreign research institutes such as the Institute of Space and Astronau-tical Science (ISAS),Tokyo,Japan,the German Aerospace Research Establish-ment (DLR),Oberpfafenhoffen,Germany,and the Jet Propulsion Laboratory (JPL),Pasadena,CA,where he received a NASA recognition for the innovative development of a ScanSAR processor for the SRTM mission.His main research activities are in the SAR data processing field as well as in IFSAR techniques.On this topic,he has authored 30international journal papers and,more recently,a book Synthetic Aperture Radar Processing (Boca Raton,FL:CRC).He also holds two patents on SAR raw data processing techniques.nari has been Chairman at several international conferences and was invited to join the technical program committee for the IGARSS Conference in 2000and2001.Manlio Tesauro received the Laurea degree (summa cum laude)in electronic engineering and the Ph.D.degree in electronic engineering and computer sci-ence,both from the University of Napoli “Federico II,”Napoli,Italy,in 1992and 1998,respectively.In 1998and 1999,he was with the Istituto di Ricerca per l’Elettromagnetismo ed I Componenti Elettronici (IRECE),Napoli,National Research Council (CNR),with a grant from Telespazio.Since 2000,he has been a Research Scientist with the Dipartimento di Ingegneria dell’Innovazione,University of Lecce,Lecce,Italy.In February 2000,he was a member of the Italian Team in the ASI Ground Data Processing Chain during the Shuttle Radar Topography Mission (SRTM)at the Jet Propulsion Laboratory,Pasadena,CA.His main interests are in the field of statistical signal processing with emphasis on SAR and IFSARprocessing.Eugenio Sansosti (M’96)received the Laurea degree (summa cum laude)in electronic engineering from the University of Napoli “Federico II,”Napoli,Italy,in 1995.Since 1997,he has been with the Istituto di Ricerca per l’Elettromagnetismo e I Componenti Elettronici (IRECE),National Research Council (CNR),where he currently holds a Full Researcher position.He is also an Adjunct Professor of electrical Communica-tions at the University of Cassino,Cassino,Italy.He was a Guest Scientist with the Jet Propulsion Labora-tory,Pasadena,CA,from August 1997to February 1998,and again in February 2000in support of the NASA Shuttle Radar Topography Mission.In November and December 2000,he worked as an Image Processing Adviser at the Istituto Tecnologico de Aeronautica (ITA),Sao Josédos Campos SP,Brazil.His main research interests are in airborne and spaceborne synthetic aperture radar (SAR)data processing,SAR interferometry,and differential SARinterferometry.Gianfranco Fornaro received the Laurea degree in electronic engineering from the University of Napoli “Federico II,”Napoli,Italy,in 1992,and the Ph.D.degree from the University of Rome “La Sapienza,”Rome,Italy,in 1997.He is currently a Full Researcher at the Istituto di Ricerca per l’Elettromagnetismo e i Componenti Elettronici (IRECE),Italian National Research Council (CNR)and Adjunct Professor of Communi-cation,University of Cassino,Cassino,Italy.He has been a Visiting Scientist with the German AerospaceEstablishment (DLR),Oberpfafenhoffen,Germany,and the Politecnico de Milano,Milano,Italy,and has been a Lecturer with the Istituto Tecnologico de Aeronautica (ITA),Sao Josédos Campos SP,Brasil.His main research interests are in the signal processing field with applications to the synthetic aperture radar (SAR)data processing,SAR interferometry,and differential SAR interferometry.Dr.Fornaro was awarded the Mountbatten Premium Award by the Institution of Electrical Engineers (IEE)in 1997.。

The Introduction of Smart Antenna

The Introduction of Smart Antenna

Modules of Smart Antenna
智能天线的模块组成
Modules of Smart Antenna
Array antenna for signal sampling
Analog-to -Dgital Converter(ADC) Intelligent pБайду номын сангаасocessing
Modules of Smart Antenna
Its function is based on the signal environment to selection criterion and algorithm weights.
Include: (1)The adaptive digital signal processor based on digital signal processor and adaptive algorithm as core is used to produce the adaptive and optimal weight coefficient . (2)Adaptive beam forming network is composed of dynamic adaptive weighted network.
What is Smart Antenna ?
Smart antenna is a bidirectional installation at the scene of the base station antenna, through a set of fixed antennas with programmable electronic phase relationship get directional unit, and can also obtain the direction of each link between base station and mobile station.Smart antenna is able to maintain the best performance of the communication system by adjusting its parameters according to the electromagnetic environment .

英语中的短线例子

英语中的短线例子

英语中的短线例子1、Alignment Control For Short-Line Precast Segmental Bridges短线法节段预制拼装桥梁线形控制探讨2、Geometric Shape Control Of Precasting Of PC Box Girder Segments By Short-Line Match Method预应力混凝土箱梁短线法节段预制线形控制3、On Box Girder Precast Segment Assembling By Short-Line Method & Alignment Control Technological Principle 短线法箱梁节段预制拼装及线形控制技术原理4、Application Of Precast Box Girder By Short Line Casting In Hong Kong Disneyland Construction Project短线法预制箱梁在香港迪士尼工程中的应用5、Sensitivity Analysis And Identification Of Parameters On Construction Control Of Short-Line Method短线法施工控制参数敏感性分析及参数识别6、Dog-Leg Spool Piece折线形法兰联接短管段7、Junction Treatment In Computation Of Short BackfireAntenna By Moment Method短背射天线矩量法计算中的结头处理8、Research On The Theory And Algorithm Of Short Spatio-Temporal Baseline PS-DInSAR;短时空基线PS-DInSAR理论及其算法研究9、The Research Of Double Scourge Antenna S Radialization On Warship Using The FDTD Method;基于FDTD法舰船短波双鞭天线场研究10、Application Of MoM/FDTD Hybrid Technique In Shortwave AntennaMoM/FDTD混合法在短波天线中的应用研究11、Solving Minimum Distance Of Two Curves Based On Genetic Algorithm基于遗传算法求解两曲线间最短距离12、Study About Test Method Of Addition Constant Of Total Station Instruments Based On The Short Baseline全站仪加常数的短基线检定方法探讨13、A Beacon Positioning Method Based On USBL一种基于超短基线的声信标定位方法14、Small Baseline DInSAR Approach With Constraints And Its Applications附加约束条件短基线DInSAR法及其应用15、Two Simple Calculation Methods Of Linear Convolution To Short Sequence短序列线性卷积的两种简便计算方法。

阿尔茨海默病的纳米疗法研究进展

阿尔茨海默病的纳米疗法研究进展
相容性
固体脂质 载体
胡椒碱固体脂质纳米粒[33] 槲皮素固体脂质纳米粒[34]
靶向性高,药物物理稳定 性强,药物释放性良好
脂质/ 脂蛋白 纳米颗粒
ApoE3-rHDL[35]
乳铁蛋白-姜黄素低密度脂蛋白 纳米粒[36]
载药能力强,稳定性高, 药物不良反应低
金属基 载体
氧化铈纳米颗粒[40] TPP-Ceria NPs[41]
大量的纳米载体和 NPs 前体药物在动物模型中的细胞 毒性可以忽略不计,纳米释药系统还可以非侵入性地将药物 递送至大脑,通过靶向给药可增强治疗 AD 的各种药物、生 物活性剂的生物利用度或生物有效性,NMs 在穿过 BBB 治
* 基金项目
作者简介 **通讯作者
收稿日期
国家重点研发计划渊2016YFC1306300冤曰国家重点研发计 划渊2018YFA0108503冤 王晓珍袁女袁研究实习员 E-mail: wxz.6016@ 王蓉袁女袁博士生导师 E-mail: wangrong@ 2020-09-30 修回日期 2021-01-11
Kulkarni PV 等[16]开发了一种基于 2-氰基丙烯酸正丁酯 的脑靶向纳米多聚体系统,包载了放射性标记的淀粉样脂肪 酸药物 125I-氯碘喹啉(CQ,5-氯-7-碘-8-羟基喹啉),用于 AD 的早期诊断,在小鼠模型中,负载的 NPs 可有效地穿过
表 1 不同类型纳米药物及其特点
NMs 类型
成螺旋片段,产生神经纤维缠结,最终导致神经元死亡。目前 发现的 Tau 蛋白磷酸化位点至少有 45 个,其中主要发生在 丝氨酸残基和苏氨酸残基的羟基上。Tau 蛋白的磷酸化受一 系列激酶的调节,包括蛋白激酶 A、糖原合成酶激酶 3茁、酪 氨酸激酶和细胞周期蛋白依赖激酶 5 等[8]。研究表明,相比 茁-淀粉样蛋白的异常沉积,Tau 蛋白的异常磷酸化所致的聚 集同 AD 的相关性更高。 1.3 小胶质细胞

智能家居 外文翻译 外文文献 英文文献

智能家居 外文翻译 外文文献 英文文献

Increasing an individual’s quality of life via their intelligent home The hypothesis of this project is: can an individual’s quality of life be increased by integrating “intelligent technology” into their home environment. This hypothesis is very broad, and hence the researchers will investigate it with regard to various, potentially over-lapping, sub-sections of the population. In particular, the project will focus on sub-sections with health-care needs, because it is believed that these sub-sections will receive the greatest benefit from this enhanced approach to housing. Two research questions flow from this hypothesis: what are the health-care issues that could be improved via “intelligent housing”, and what are the technological issues needing to be sol ved to allow “intelligent housing” to be constructed? While a small number of initiatives exist, outside Canada, which claim to investigate this area, none has the global vision of this area. Work tends to be in small areas with only a limited idea of how the individual pieces contribute towards a greater goal. This project has a very strong sense of what it is trying to attempt, and believes that without this global direction the other initiatives will fail to address the large important issues described within various parts of this proposal, and that with the correct global direction the sum of the parts will produce much greater rewards than the individual components. This new field has many parallels with the field of business process engineering, where many products fail due to only considering a sub-set of the issues, typically the technology subset. Successful projects and implementations only started flow when people started to realize that a holistic approach was essential. This holistic requirement also applies to the field of “smart housing”; if we genuinely want it to have benefit to the community rather than just technological interest. Having said this, much of the work outlined below is extremely important and contains a great deal of novelty within their individual topics.Health-Care and Supportive housing:To date, there has been little coordinated research on how “smart house” technologies can assist frail seniors in remaining at home, and/or reduce the costs experienced by their informal caregivers. Thus, the purpose of the proposed research is to determine the usefulness of a variety of residential technologies in helping seniors maintain their independence and in helping caregivers sustain their caringactivities.The overall design of the research is to focus on two groups of seniors. The first is seniors who are being discharged from an acute care setting with the potential for reduced ability to remain independent. An example is seniors who have had hip replacement surgery. This group may benefit from technologies that would help them become adapted to their reduced mobility. The second is seniors who have a chronic health problem such as dementia and who are receiving assistance from an informal caregiver living at a distance. Informal caregivers living at a distance from the cared-for senior are at high risk of caregiver burnout. Monitoring the cared-for senior for health and safety is one of the important tasks done by such caregivers. Devices such as floor sensors (to determine whether the senior has fallen) and access controls to ensure safety from intruders or to indicate elopement by a senior with dementia could reduce caregiver time spent commuting to monitor the senior.For both samples, trials would consist of extended periods of residence within the ‘smart house’. Samples of seniors being discharged from acute care would be recruited from acute care hospitals. Samples of seniors being cared for by informal caregivers at a distance could be recruited through dementia diagnosis clinics or through request from caregivers for respite.Limited amounts of clinical and health service research has been conducted upon seniors (with complex health problems) in controlled environments such as that represented by the “smart house”. For exa mple, it is known that night vision of the aged is poor but there is very little information regarding the optimum level of lighting after wakening or for night activities. Falling is a major issue for older persons; and it results in injuries, disabilities and additional health care costs. For those with dementing illnesses, safety is the key issue during performance of the activities of daily living (ADL). It is vital for us to be able to monitor where patients would fall during ADL. Patients and caregivers activities would be monitored and data will be collected in the following conditions.Projects would concentrate on sub-populations, with a view to collecting scientific data about their conditions and the impact of technology upon their life styles. For example:Persons with stable chronic disability following a stroke and their caregivers: to research optimum models, types and location of various sensors for such patients (these patients may have neglect, hemiplegia, aphasia and judgment problems); to research pattern of movements during the ambulation, use of wheel chairs or canes on various type of floor material; to research caregivers support through e-health technology; to monitor frequencies and location of the falls; to evaluate the value of smart appliances for stroke patients and caregivers; to evaluate information and communication technology set up for Tele-homecare; to evaluate technology interface for Tele-homecare staff and clients; to evaluate the most effective way of lighting the various part of the house; to modify or develop new technology to enhance comfort and convenience of stroke patients and caregivers; to evaluate the value of surveillance systems in assisting caregivers.Persons with Alzheimer’s disease and their caregivers: to evaluate the effect of smart house (unfamiliar environment) on their ability to conduct self-care with and without prompting; to evaluate their ability to use unfamiliar equipment in the smart house; to evaluate and monitor persons with Alzheimer’s diseas e movement pattern; to evaluate and monitor falls or wandering; to evaluate the type and model of sensors to monitor patients; to evaluate the effect of wall color for patients and care givers; to evaluate the value of proper lighting.Technology - Ubiquitous Computing:The ubiquitous computing infrastructure is viewed as the backbone of the “intelligence” within the house. In common with all ubiquitous computing systems, the primary components with this system will be: the array of sensors, the communication infrastructure and the software control (based upon software agents) infrastructure. Again, it is considered essential that this topic is investigated holistically.Sensor design: The focus of research here will be development of (micro)-sensors and sensor arrays using smart materials, e.g. piezoelectric materials, magneto strictive materials and shape memory alloys (SMAs). In particular, SMAs are a class of smart materials that are attractive candidates for sensing and actuating applications primarily because of their extraordinarily high work output/volume ratiocompared to other smart materials. SMAs undergo a solid-solid phase transformation when subjected to an appropriate regime of mechanical and thermal load, resulting in a macroscopic change in dimensions and shape; this change is recoverable by reversing the thermo mechanical loading and is known as a one-way shape memory effect. Due to this material feature, SMAs can be used as both a sensor and an actuator.A very recent development is an effort to incorporate SMAs in micro-electromechanical systems (MEMS) so that these materials can be used as integral parts of micro-sensors and actuators.MEMS are an area of activity where some of the technology is mature enough for possible commercial applications to emerge. Some examples are micro-chemical analyzers, humidity and pressure sensors, MEMS for flow control, synthetic jet actuators and optical MEMS (for the next generation internet). Incorporating SMAs in MEMS is a relatively new effort in the research community; to the best of our knowledge, only one group (Prof. Greg Carman, Mechanical Engineering, University of California, Los Angeles) has successfully demonstrated the dynamic properties of SMA-based MEMS. Here, the focus will be to harness the sensing and actuation capabilities of smart materials to design and fabricate useful and economically viable micro-sensors and actuators.Communications: Construction and use of an “intelligent house” offers extensive opportunities to analyze and verify the operation of wireless and wired home-based communication services. While some of these are already widely explored, many of the issues have received little or no attention. It is proposed to investigate the following issues:Measurement of channel statistics in a residential environment: knowledge of the indoor wireless channel statistics is critical for enabling the design of efficient transmitters and receivers, as well as determining appropriate levels of signal power, data transfer rates, modulation techniques, and error control codes for the wireless links. Interference, channel distortion, and spectral limitations that arises as a result of equipment for the disabled (wheelchairs, IV stands, monitoring equipment, etc.) is of particular interest.Design, analysis, and verification of enhanced antennas for indoor wirelesscommunications. Indoor wireless communications present the need for compact and rugged antennas. New antenna designs, optimized for desired data rates, frequency of operation, and spatial requirements, could be considered.Verification and analysis of operation of indoor wireless networks: wireless networking standards for home automation have recently been commercialized. Integration of one or more of these systems into the smart house would provide the opportunity to verify the operation of these systems, examine their limitations, and determine whether the standards are over-designed to meet typical requirements.Determination of effective communications wiring plans for “smart homes.”: there exist performance/cost tradeoffs regarding wired and wireless infrastructure. Measurement and analysis of various wireless network configurations will allow for determination of appropriate network designs.Consideration of coordinating indoor communication systems with larger-scale communication systems: indoor wireless networks are local to the vicinity of the residence. There exist broader-scale networks, such as the cellular telephone network, fixed wireless networks, and satellite-based communication networks. The viability and usefulness of compatibility between these services for the purposes of health-care monitoring, the tracking of dementia patients, etc needs to be considered.Software Agents and their Engineering: An embedded-agent can be considered the equivalent of supplying a friendly expert with a product. Embedded-agents for Intelligent Buildings pose a number of challenges both at the level of the design methodology as well as the resulting detailed implementation. Projects in this area will include:Architectures for large-scale agent systems for human inhabited environment: successful deployment of agent technology in residential/extended care environments requires the design of new architectures for these systems. A suitable architecture should be simple and flexible to provide efficient agent operation in real time. At the same time, it should be hierarchical and rigid to allow enforcement of rules and restrictions ensuring safety of the inhabitants of the building system. These contradictory requirements have to be resolved by designing a new architecture that will be shared by all agents in the system.Robust Decision and Control Structures for Learning Agents: to achieve life-long learning abilities, the agents need to be equipped with powerful mechanisms for learning and adaptation. Isolated use of some traditional learning systems is not possible due to high-expected lifespan of these agents. We intend to develop hybrid learning systems combining several learning and representation techniques in an emergent fashion. Such systems will apply different approaches based on their own maturity and on the amount of change necessary to adapt to a new situation or learn new behaviors. To cope with high levels of non-determinism (from such sources as interaction with unpredictable human users), robust behaviors will be designed and implemented capable of dealing with different types of uncertainty (e.g. probabilistic and fuzzy uncertainty) using advanced techniques for sensory and data fusion, and inference mechanisms based on techniques of computational intelligence.Automatic modeling of real-world objects, including individual householders: The problems here are: “the locating and extracting” of information essential for representation of personality and habits of an individual; development of systems that “follow and adopt to” individual’s mood and behavior. The solutions, based on data mining and evolutionary techniques, will utilize: (1) clustering methods, classification tress and association discovery techniques for the classification and partition of important relationships among different attributes for various features belonging to an individual, this is an essential element in finding behavioral patterns of an individual; and (2) neuro-fuzzy and rule-based systems with learning and adaptation capabilities used to develop models of an individual’s characteristics, this is essential for estimation and prediction of potential activities and forward planning.Investigation of framework characteristics for ubiquitous computing: Consider distributed and internet-based systems, which perhaps have the most in common with ubiquitous computing, here again, the largest impact is not from specific software engineering processe s, but is from available software frameworks or ‘toolkits’, which allow the rapid construction and deployment of many of the systems in these areas. Hence, it is proposed that the construction of the ubiquitous computing infrastructure for the “smart house” should also be utilized as a software engineering study. Researchers would start by visiting the few genuine ubiquitous computing systems inexistence today, to try to build up an initial picture of the functionality of the framework. (This approach has obviously parallels with the approach of Gamma, Helm, Johnson and Vlissides deployed for their groundbreaking work on “design patterns”. Unfortunately, in comparison to their work, the sample size here will be extremely small, and hence, additional work will be required to produce reliable answers.) This initial framework will subsequently be used as the basis of the smart house’s software system. Undoubtedly, this initial framework will substantially evolve during the construction of the system, as the requirements of ubiquitous computing environment unfold. It is believed that such close involvement in the construction of a system is a necessary component in producing a truly useful and reliable artifact. By the end of the construction phase, it is expected to produce a stable framework, which can demonstrate that a large number of essential characteristics (or patterns) have been found for ubiquitous computing.Validation and Verification (V&V) issues for ubiquitous computing: it is hoped that the house will provide a test-bed for investigating validation and verification (V&V) issues for ubiquitous computing. The house will be used as an assessment vehicle to determine which, if any, V&V techniques, tools or approaches are useful within this environment. Further, it is planned to make this trial facility available to researchers worldwide to increase the use of this vehicle. In the long-term, it is expected that the facilities offered by this infrastructure will evolve into an internationally recognized “benchmarking” site for V&V activities in ubiquitous computing.Other technological areas:The project also plans to investigate a number of additional areas, such as lighting systems, security systems, heating, ventilation and air conditioning, etc. For example, with regard to energy efficiency, the project currently anticipates undertaking two studies:The Determination of the effectiveness of insulating shutters: Exterior insulating shutters over time are not effective because of sealing problems. Interior shutters are superior and could be used to help reduce heat losses. However, their movement and positioning needs appropriate control to prevent window breakage due to thermalshock. The initiation of an opening or closing cycle would be based on measured exterior light levels; current internal heating levels; current and expected use of the house by the current inhabitants, etc.A comparison of energy generation alternatives: The energy use patterns can easily be monitored by instrumenting each appliance. Natural gas and electricity are natural choices for the main energy supply. The conversion of the chemical energy in the fuel to heat space and warm water can be done by conventional means or by use of a total energy system such as a V olvo Penta system. With this system, the fuel is used to power a small internal combustion engine, which in turn drives a generator for electrical energy production. Waste heat from the coolant and the exhaust are used to heat water for domestic use and space heating. Excess electricity is fed back into the power grid or stored in batteries. At a future date, it is planned to substitute a fuel cell for the total energy system allowing for a direct comparison of the performance of two advanced systems.Intelligent architecture: user interface design to elicit knowledge modelsMuch of the difficulty in architectural design is in integrating and making explicit the knowledge of the many converging disciplines (engineering, sociology, ergonomic sand psychology, to name a few), the building requirements from many view points, and to model the complex system interactions. The many roles of the architect simply compound this. This paper describes a system currently under development—a 3Ddesign medium and intelligent analysis tool, to help elicit and make explicit these requirements. The building model is used to encapsulate information throughout the building lifecycle, from inception and master planning to construction and ‘lived-in’ use. From the tight relationship between m aterial behaviour of the model, function analysis and visual feedback, the aim is to help in the resolution of functional needs, so that the building meets not only the aims of the architect, but the needs of the inhabitants, users and environment.The Problem of Designing the Built Environment:It is often said that architecture is the mother of the arts since it embodies all the techniques of painting: line, colour, texture and tone, as well as those of sculpture: shape, volume, light and shadow, and the changing relative position of the viewer, andadds to these the way that people inhabit and move through its space to produce—at its best—a spectacle reminiscent of choreography or theatre. As with all the arts, architecture is subject to personal critical taste and yet architecture is also a public art, in that people are constrained to use it. In this it goes beyond the other arts and is called on to function, to modify the climate, provide shelter, and to subdivide and structure space into a pattern that somehow fits the needs of social groups or organizations and cultures. Whilst architecture may be commissioned in part as a cultural or aesthetic expression, it is almost always required to fulfill a comprehensive programme of social and environmental needs.This requirement to function gives rise to three related problems that characterize the design and use of the built environment. The first depends on the difference between explicit knowledge—that of which we are at least conscious and may even have a scientific or principled understanding—and implicit knowledge, which, like knowing your mother tongue, can be applied without thinking. The functional programmes buildings are required to fulfill are largely social, and are based on implicit rather than explicit bodies of knowledge. The knowledge we exploit when we use the built environment is almost entirely applied unconsciously. We don’t have to think about buildings or cities to use them; in fact, when we become aware of it the built environment is often held to have failed. Think of the need for yellow lines to help people find their way around the Barbican complex in the City of London, or the calls from tenants to ‘string up the architects’ when housing estates turn out to be social disasters.The second is a problem of complexity. The problem is that buildings need to function in so many different ways. They are spatial and social, they function in terms of thermal environment, light and acoustics, they use energy and affect people’s health, they need to be constructed and are made of physical components that can degrade and need to be maintained. On top of all this they have an aesthetic and cultural role, as well as being financial investments and playing an important role in the economy. Almost all of these factors are interactive—decisions taken for structural reasons have impacts on environment or cost—but are often relatively independent in terms of the domains ofknowledge that need to be applied. This gives rise to a complex design problem in which everything knocks on to everything else, and in which no single person has a grasp of all the domains of knowledge required for its resolution. Even when the knowledge that needs to be applied is relatively explicit—as for instance in structural calculations, or thoseconcerning thermal performance—the complex interactive nature of buildings creates a situation in which it is only through a team approach that design can be carried out, with all that this entails for problems of information transfer and breakdowns in understanding.The third is the problem of ‘briefing’. It is a characteristic of building projects that buildings tend not to be something that people buy ‘off-the-shelf’. Often the functional programme is not even explicit at the outset. One might characterise the process that actually takes place by saying that the design and the brief ‘co-evolve’. As a project moves from inception to full sp ecification both the requirements and the design become more and more concrete through an iterative process in which design of the physical form and the requirements that it is expected to fulfill both develop at once. Feasible designs are evaluated according to what they provide, and designers try to develop a design that matches the client’s requirements. Eventually, it is to be hoped, the two meet with the textual description of what is required and the physical description of the building that will provide it more or less tying together as the brief becomes a part of the contractual documentation that theclient signs up to.These three problems compound themselves in a number of ways. Since many of the core objectives of a client organization rest on implicit knowledge—the need for a building to foster communication and innovation amongst its workers for instance—it is all too easy for them to be lost to sight against the more explicitly stated requirements such as those concerned with cost, environmental performance or statutory regulations. The result is that some of the more important aspects of the functional programme can lose out to less important but better understood issues. This can be compounded by the approach that designers take in order to control themcomplexity of projects. All too often the temptation is to wait until the general layout of a building is ‘fixed’ before calling in the domain experts. The result is that functional design has to resort to retrofitting to resolve problems caused by the strategic plan.The Intelligent Architecture project is investigating the use of a single unified digital model of the building to help resolve these problems by bringing greater intelligence to bear at the earliest ‘form generating’ phase of the design process when the client’s requirements are still being specified and when both physical design and client expectations are most easily modified. The aim is to help narrow the gap between what clients hope to obtain and what they eventually receive from a building project.The strategy is simple. By capturing representations of the building as a physical and spatial system, and using these to bring domain knowledge to bear on a design at its earliest stages, it is hoped that some of the main conflicts that lead to sub- optimal designs can be avoided. By linking between textual schedules of requirements and the physical/spatial model it is intended to ease the reconciliation of the brief and the design, and help the two to co-evolve. By making available some of the latest ‘intelligent’ techniques for modelling spatial systems in the built environment, it is hoped to help put more of the implicit knowledge on an equal footing with explicit knowledge, and by using graphical feedback about functional outcomes where explicit knowledge exists, to bring these within the realm of intuitive application by designers.The Workbench:In order to do this, Intelligent Architecture has developed Pangea. Pangea has been designed as a general-purpose environment for intelligent 3D modelling—it does not pre-suppose a particular way of working, a particular design solution, or even a particular application domain. Several features make this possible.Worlds can be constructed from 3D and 2D primitives (including blocks, spheres, irregular prisms and deformable surfaces), which can represent real-world physical objects, or encapsulate some kind of abstract behaviour. The 3D editor provides a direct and simple interface for manipulating objects—to position, reshape, rotate andrework. All objects, both physical and abstract, have an internal state (defined by attributes), and behaviour, rules and constraints (in terms of a high-level-language ‘script’). Attributes can be added dynamically, making it possible for objects to change in nature, in response to new knowledge about them, or to a changing environment. Scripts are triggered by events, so that objects can respond and interact, as in the built environment, molecular systems, or fabric falling into folds on an irregular surface.Dynamic linking allows Pangea’s functionality to be extended to include standard ‘off-the-peg’ software tools —spreadsheets, statistical analysis applications, graphing packages and domain-specific analysis software, such as finite element analysis for air- flow modelling. The ‘intelligent toolkit’ includes neural networks [Koho89] [Wass89], genetic algorithms [Gold89] [Holl75] and other stochastic search techniques [KiDe95], together with a rule- based and fuzzy logic system [Zade84]. The intelligent tools are objects, just like the normal 3D primitives: they have 3D presence and can interact with other 3D objects. A natural consequence of this design is easy ‘hybridisability’ of techniques, widely considered as vital to the success of intelligent techniques in solving realistically complex problems [GoKh95]. This infrastructure of primitive forms, intelligent techniques and high-level language makes it possible to build applications to deal with a broad range of problems, from the generation of architectural form, spatial optimisation, object recognition and clustering, and inducing rules and patterns from raw data.Embedding Intelligence:Many consider that there is an inevitable trade-off between computers as a pure design medium, and computers with intelligence, ‘as a thinking machine’ [Rich94]. We propose here that it is possible to provide both these types of support, and allow the user to choose how best to use each, or not, according to the situation.It is essential that the creative role of the architect is preserved as he or she uses the work bench, that the architect as artist may draw manipulate the world as seen through the workbench as freely as they would when using a sheet of paper. Much of。

多输入多输出通信系统的信道模型及容量

多输入多输出通信系统的信道模型及容量

多输入多输出通信系统的信道模型及容量专业:通信工程摘要随着无线通信事业的迅速发展,用户对无线通信的速率和服务质量提出了越来越高的要求。

然而频谱资源的匮乏限制了无线通信的进一步发展;另一方面,无线信道的多径传播特性和时变特性会对其中传输的信号带来非常大的损害。

近年来多输入天线多输出天线(MIMO)技术因为能大幅度增加无线通信系统的谱效率和提高传输可靠性而得到了越来越多的关注。

MIMO多天线系统所提供的空间复用增益和空间分集增益可以极大地提高无线链路的容量和质量。

现有的研究成果己经表明,MIMO所能达到的极高的频谱效率是目前任何一种无线技术所不及的,因此它被认为是未来新一代移动通信系统的备选关键技术之一。

根据信道的输入输出情况,使用多天线技术的通信系统可以分为单输入多输出SI MO(Single-InputMultiple-Output)系统、多输入单输出MISO(Multiple-Input Single-Output)系统,以及多输入多输出MIMO(Multiple-InputMultiple-Output)系统三种类型。

本文首先介绍了MIMO系统的基本概念和信道模型,然后我们从信息论的角度,根据传统SISO信道的香农容量,推导出MIMO信道容量公式,并且依次推导出SIMO信道和MISO信道的容量。

本文对MIMO信道模型和信道容量的研究表明,MIMO技术对于未来新一代无线通信具有极其的重要意义。

关键词:MIMO,SIMO,MISO,多天线系统,信道模型,信道容量。

Channel Modeland Capacity of the MIMO CommunicationSystemsAbstractAs the wireless communicationmakes rapid progress, thedemand for higher data ratesandhigherqualityin wireless communicat ionsystems has recently seen unprecedented growth.However, one of the most limiting factors in growthofwireless communications is thescarcity ofspectrum.In addition, the multi-path propagation andtime variance characteristics of wireless channel bring some impairment to the signals transmitted overit. Inrecent years, multiple input multiple output(MIMO) antennas techniquehas received more and more attention,asit can dramatically increase thespectral efficiency and improvethe transmissionreliabilityof wireless communication systems. The MIMO channel gainof MIMO syst emsthat include spatialmultiplexing (SM)gain and the spatialdiversity (SD) gaincanincreasegreatly the capacityand the qualityof the wirelesslink,andthe research resultsshow spectral efficiency ofMIMO technique ishigher than any otherexistingwireless techniques. SoMIMO technique isconsidered as one of candid acy techniques thatcan be used inthenext new generationof mobile cellular communication systems.Any given communication systemthatutilizes the multiple antenna techniquecan be classified into threecategories: single input multiple output(SIMO), multiple input singleoutput(MISO)andmultiple input multiple output (MIMO) system respectively. This paper firstlyintroduces the basic concept and model of MIMO channel.Secondly,i nthe view of information theory,according totraditionalSISO chan nel Shannoncapacity, we derived thecapacity of MIMOchannel, MISO channeland SIMOchannel.In thispaper, thestudies on MIMO channel modeland channel capacityshowthat MIMO techniqueisvitaltothe new gener ationof wireless communications.Keywords: MIMO, SIMO, MISO,Multiple Antenna System,Channel Model,Channel Capacity.目录摘要ﻩ错误!未定义书签。

antenna_downtilt

antenna_downtilt

Optimum Antenna Downtilt Angles for Macrocellular WCDMA networkJarno Niemel¨a,Tero Isotalo,and Jukka Lempi¨a inenAbstractThe impact of antenna downtilt on the performance of cellular WCDMA network has been studied by using a radio network planning tool.An optimum downtilt angle has been evaluated for a numerous practical macrocellular site and antenna configurations for electrical and mechanical antenna downtilt concepts.The aim of this massive simulation campaign was expected to provide an answer to two questions:firstly,how to selected the downtilt angle of a macrocellular base station antenna,and secondly,what is the impact of antenna downtilt on system capacity and network coverage.Optimum downtilt angles were observed to vary between3.5◦–10.5◦depending on the network configuration.Moreover,the corresponding downlink capacity gains varied between 0–58%.Antenna vertical beamwidth affects clearly the required optimum downtilt angle the most.On the other hand,with wider antenna vertical beamwidth the impact of downtilt on system performance is not such imposing.In addition,antenna height together with the size of the dominance area affect the required downtilt angle.Finally, the simulation results revealed how the importance of the antenna downtilt becomes more significant in dense networks,where the capacity requirements are typically also higher.Index TermsElectrical downtilt,other-cell interference,mechanical downtilt,network coverage,system capacity,WCDMAI.I NTRODUCTIONThe majority of the current third generation mobile communication systems uses CDMA(code division multiple access)technique as multiple access method.Due to its interference-limited nature,the system capacity of any cellular CDMA network is vulnerable to any additional other-cell interference.Therefore,in a CDMA radio network planning process,the main target is to plan the network in such a manner that other-cell interference is minimized in order to be able to maximize the system capacity.This can be achieved,among all other techniques,by optimizing the network topology.One important phase of the topology planning1is the definition of antenna configuration,and especially,antenna downtilt angle.By utilizing antenna downtilt, signal level within a cell can be improved and interference radiation towards other cells effectively reducedThis work was supported by the European Communications Engineering(ECE)Ltd.,Nokia Networks,FM Kartta,and National Technology Agency of Finland.J.Niemel¨a,T.Isotalo,and J.Lempi¨a inen are with Tampere University of Technology,P.O.BOX553,33101Tampere,Finland(phone: +358-3-31154749;fax:+358-3-31153808;e-mail:fistname@tut.fi).1The target of topology planning is to optimize site and antenna configuration in such a manner that cells become as isolated as possible.due to more precise aiming of the antenna radiation pattern.However,an excessive downtilt angle might lead to coverage problems at cell border areas.Therefore,it is vital to define an optimum downtilt angle separately for each site and antenna configuration.Antenna downtilt includes two different concepts—mechanical downtilt(MDT)and electrical downtilt(EDT). Utilization of antenna mechanical downtilt has been a tool for radio network planners to optimize networks. It has been observed to be an efficient method to reduce other-cell interference in the main-lobe direction[1]. Hence,MDT is widely used in TDMA/FDMA(time division multiple access/frequency division multiple access)networks as in GSM(Global System for Mobile Communications)to decrease co-channel interference. However,in GSM,utilization of downtilt targets in achieving a smaller frequency reuse factor.Therefore,any improvements in the radio network quality due to antenna downtilt have not been directly taken into account in capacity or frequency planning phases in practice,but have been used as an extra margin to avoid serious interference areas[2].Nevertheless,capacity gains up to20%have been reported from utilization of MDT in GSM networks[3].Th´ıs reduction of other-cell interference affects especially in macrocellular WCDMA (wideband CDMA)networks[4],where the achievable capacity gain from MDT has been observed to vary between15%and20%[5]–[7].Moreover,MDT is able to enhance system capacity in microcellular environment [8]–[9],even though the contribution of other-cell interference is typically smaller in microcellular environment. In an interference-limited WCDMA system,suppression of side and back lobes of an antenna would be advantageous due to further reduction of other-cell interference.Therefore,electrically downtilted antennas might become an attractive choice for antenna selection.In EDT,the vertical radiation pattern is uniformly downtilted in all horizontal directions—contrary to mechanical downtilt.Prior work[10]have reported capacity gains up to50%and20%for3-sectored and6-sectored sites,respectively,with corresponding optimum downtilt angles of7◦–10◦.On the contrary,in[11],optimum EDT angles have been defined site-by-site basis using an iterative algorithm.Moreover,optimum downtilt angles were found to vary between6◦–8◦,and to provide capacity gain up to15%with practical macrocellular network configurations.Naturally,an increasing impact of EDT on the system capacity have been observed in microcellular environment as well[12].Recently,one direction of research concerning antenna downtilt has been concentrated on adaptively and remotely controlled EDT according to changes in the load or user distribution within a cell[13].Compared to utilization of a static network-wide downtilt angle,dynamically changing downtilt angle can further boost the system capacity by 20–30%under certain circumstances[14].The aim of this paper is to extend the prior work of the authors in[7]and[15],and to present a simultaneous analysis of mechanical and electrical antenna downtilt concepts in WCDMA macrocellular network,and to evaluate optimum downtilt angles for different practical base station site and antenna configurations for suburban environment by utilizing a static radio network planning tool.Furthermore,the target is to identify and analyze the most important phenomena resulting from utilization of antenna downtilt,and to clarify the sensitivity of the selection of downtilt angle.Finally,capacity gains of network-wide static antenna downtilt are provided for all simulated network configurations.II.C APACITY OF WCDMA N ETWORKIn cellular WCDMA system,the same carrier frequency is used in all cells,and users are separated by unique code sequences.The capacity of WCDMA system is thus typically interference-limited rather than blocking-limited,since all mobiles and base stations interfere each others in uplink and downlink directions. Furthermore,the network(or cell)capacity is defined by the load equations that,on the other hand,set limits for the maximum number of users in a cell or for the maximum cell throughput.The system capacity is defined in this context as the maximum number of users that can be supported simultaneously with a pre-defined service probability target.A.Uplink CapacityEnergy per bit to noise spectral density ratio,E b/N0,is used to measure the quality of a connection.In uplink(UL)direction,the signal quality received at the base station for the j th user must satisfy the following condition:E b N0j=WR jp tx,jP bs rx L j−p tx,j(1)where W is the system chip rate,R j is the bit rate of the j th mobile,p tx,j is the transmit(TX)power of the j th mobile,P bs rx is the total received wideband power2at the base station,and L j is the uplink path loss from the j th mobile to the base station.The maximum uplink capacity is defined by the uplink load factor,ηUL,which is given as interference rise above the thermal noise power:ηUL=P bs rx−p nP rx(2)where p n is the thermal noise power at the base station.The load factor is used to define a radio network planning parameter called interference margin3(IM)that takes into account the changes in the network coverage due to cell breathing:IM=−10log10(1−ηUL)(3)B.Downlink CapacityThe capacity of the downlink(DL)in WCDMA system behaves differently compared to the uplink.This is caused by the fact that all mobiles share the same transmit power of a base station sector.Furthermore, simultaneous transmission allows the usage of orthogonal codes.However,the code orthogonalityαis partly destroyed by multipath propagation,which depends on the propagation environment,mobile speed,and mobile location.In order to satisfy the E b/N0requirement of the k th mobile in the DL,the following criteria has to be fulfilled:2The total wideband power includes thermal noise,and received powers from mobiles in own cell as well as from other cells.3Interference margin is also called noise rise.E b N0k=WR kp tch,kP msrxL k−αP tottx−(1−α)p tch,k(4)In(4),p tch,k is the downlink traffic channel(TCH)TX power for the k th connection,P msrxis the total receivedwideband power at the mobile station,L k is the downlink path loss,and P tottxis the total TX power of a basestation sector mobile is connected to.The parameter P tottxincludes the TX power of common pilot channel(CPICH),other common channels(CCCH),and traffic channels as well.The total transmit power P tottch,mfor the TCH of the m th base station sector is thus the sum of all K connections(including soft and softer handover connections):P tot tch,m =Kk=1p tch,k(5)The downlink load factor,ηDL,is defined with the aid of the average transmit power of TCHs of base stations for a cluster of cells:ηDL= Mm=1P tottch,mMP maxtch,m(6)where M is the number of sectors in the cluster.The downlink capacity is maximized when the minimumηDL is achieved with the same number of served users K.III.A NTENNA D OWNTILTA.Downtilt ConceptsIn mechanical downtilt(MDT),the antenna element is physically directed towards the ground.Naturally,the areas near the base station experience better signal level due to the fact that antenna main lobe is more precisely directed towards the intended dominance(serving)area.However,the effective downtilt angle corresponds to the physical one only exactly in the main lobe direction,and decreases as a function of horizontal direction in such a way that the antenna radiation pattern is not downtilted at all in the side lobe direction[1].Nevertheless, interference radiation towards other cells is reduced in the main lobe direction.The relative widening of the horizontal radiation pattern is illustrated in Fig.1(a)for a horizontally65◦and vertically6◦wide antenna beam as a function of increasing downtilt angle.The reduction of the antenna gain towards the boresight,e.g.,with 8◦downtilt angle,is as large as25dB,whereas towards60◦angle the reduction is less than10dB.As the downtilt angle increases,the soft handover(SHO)probability in the cell border areas decreases[16]. On the other hand,the relative widening of the horizontal radiation pattern increases the overlapping between adjacent sectors,which makes softer handovers(SfHO)more attractive.This increase of softer handovers as a function of downtilt angle depends on sector overlapping(i.e.,sectoring and antenna horizontal beamwidth).[7],[17]Antenna electrical downtilt(EDT)is carried out by adjusting the relative phases of antenna elements of an antenna array in such a way that the radiation pattern can be downtilted uniformly in all horizontal directions [18].This technique changes slightly the vertical radiation pattern depending on the chosen EDT angle.Fig.1(b)Fig.1.The impact of antenna(a)mechanical and(b)electrical downtilt on the horizontal(azimuthal)radiation pattern in the boresight. Antenna gain is normalized to zero and the scale is in decibels.’Uptilt’of back lobe direction for mechanical downtilt is not illustrated.illustrates the behavior of the horizontal radiation pattern for65◦and vertically6◦wide antenna beam.EDT reduces efficiently radiation also towards the adjacent sectors,since all directions are downtilted uniformly. However,the coverage in the side lobe direction reduces rapidly as well,which deteriorates the network performance if antennas are downtilted excessively.Naturally,SHO probability decreases as the downtilt angle increases,whereas SfHO probability should not change remarkably.[15],[17]B.Downtilt SchemesFundamentally,there are two concepts for downtilt—mechanical and electrical.However,there exist many different tilting schemes including purely mechanical tilt,fixed electrical tilt,variable electrical tilt(VET),remote electrical tilt(RET),and continuously adjustable electrical downtilt(CAEDT).Adjusting antenna mechanical downtilt angle requires a site visit,which makes the adjustment process of tilt angles more expensive and time consuming.Hence,if MDT is utilized,the importance of the selection of an optimum mechanical tilt angle in the network deployment phase should be in great importance.Fixed electrical tilt antennas require also a site visit in order to change the tilt angle.However,if thefixed electrical tilt angle is wanted to change electrically, it requires a totally new antenna or tilt angle is further increased/decreased purely mechanically(combined tilt scheme).In VET antennas,an electrical downtilt angle is adjustable in the dynamic range of downtilt angle.A typical range for tilt angles for macrocellular antennas vary from0◦to12◦depending on the vertical beamwidth [19]–[20].Utilization of RET scheme removes the need for a site visit,since tilt angles can be changed from network management system.Hence,it saves the costs and time in optimization during network evolution.An improvement of RET scheme is CAEDT scheme,in which downtilt angle can be changed continuously and remotely according to changes,e.g.,in propagation environment or in load distribution of a cell.Nevertheless, no matter what is the utilized downtilt scheme,knowledge about the initial optimum downtilt angle is needed in order to maximize the capacity and quality.C.Selection of Downtilt AngleThe selection of antenna downtilt angle depends on the site and antenna configuration,and hence it has to be set site-by-site basis in practice.In WCDMA,an optimum downtilt angle is obviously a trade-off between other-cell interference mitigation and coverage thresholds.The optimum downtilt angle is achieved if other-cell interference is reduced to the minimum achievable level while still providing the target coverage.An optimum downtilt angle—either for MDT or EDT—depends partly on the same factors.Perhaps two most obvious ones are the geometrical factor(θgeo)and antenna vertical beamwidth factor(θbw ver).The geometrical factor takes into account the average height difference between the base station(h bs)and mobile station antenna (h ms)as well as the size of the sector dominance area(d):θgeo=arctanh bts−h msd(7)Intuitively,an increase of the antenna height should also increase the required downtilt angle and vice versa. Correspondingly,a cell with a small dominance area should require a larger downtilt angle.However,the geometrical factor as such is not enough to define the required downtilt angle,as it does not take into account any information about antenna vertical beamwidth.One possibility is to select the antenna beamwidth factor as half of the antenna half-power(−3dB)vertical beamwidth(θ−3dB).Thus,the selection of geometrical downtilt angle(νgeo)could be performed as in[21]:νgeo=θgeo+θ−3dB2(8)IV.S IMULATIONSwork ConfigurationThe impact of different network configurations on the optimum downtilt angles is simulated by using a static WCDMA radio network simulator that utilizes Monte Carlo technique for capacity and performance analysis. For the system level analysis,a macrocellular network is configured in a shape of a regular hexagonal grid of 19base stations.The selected antenna heights–25m,35m,and45m–exceed the average roof-top level that dominates in the simulation area.The site spacings in the simulations are1.5km,2.0km,and2.5km.The sectoring schemes adopted in the simulation are3-sectored and6-sectored sites.Moreover,the base station antennas are oriented to have equal directions(see Fig.2).For the3-sectored sites,the horizontal beamwidth (BW)of the antennas is65◦and vertical one either6◦or12◦with corresponding antenna gains of18dBi and 15.2dBi.On the contrary,for the6-sectored sites,horizontally33◦beamwidth and vertically6◦beamwidth antennas are utilized with corresponding antenna gain of21dBi.All radiation patterns of the base station antennas are adopted from[19].Finally,the selected site and antenna configurations are the following4:•EDT3-sectored sites with65◦/6◦•EDT3-sectored sites with65◦/12◦465◦/6◦denotes horizontal/vertical half-power beamwidth.Fig.2.A3-sectored hexagonal grid of19base stations with2.0km site spacing over the digital map.A6-sectored configuration is formed basis on3-sectored antenna directions by adding antennas between the3-sectored antennas.Traffic is distributed only inside the large hexagon.•EDT6-sectored sites with33◦/6◦•MDT3-sectored sites with65◦/6◦•MDT3-sectored sites with65◦/12◦•MDT6-sectored sites with33◦/6◦Morphological and topographic information of the simulation area is defined by a high resolution(5m x5m) digital map.The digital map includes the basic terrain types(water,open,and forest)and buildings of different heights in a raster format.The simulation area is suburban area consisting mainly of low-height residential buildings,but also including some higher commercial buildings.The simulation area of2.0km site spacing with3-sectored sites is depicted in Fig.2.B.Simulation ParametersThe simulations consist of coverage predictions and capacity analysis.First,a coverage map of the simulation area is created by using extended COST-231-Hata propagation model for each base station site configuration. The model is roughly tuned for the simulation area.The radio propagation slope of COST-231-Hata model is set to35dB/dec(25m antenna height as reference)and the mobile station antennas to1.5m.The utilized area correction factor for different clutter types are shown in Table I.Moreover,diffraction losses are modeled with Deygout model embedded in the propagation model.In the capacity analysis during Monte Carlo process,a large number of randomized snapshots are taken inM ORPHOLOGICAL CORRECTION FACTORS FOR EXTENDED COST-231-H ATA MODEL FOR DIFFERENT CLUTTER TYPES.Morphotype Correction factor[dB]Open−17Water−24Forest−10Building height<8m−4Building height>8m−3Building height>15m0Building height>23m3order to simulate service establishments in the network.The total number of mobiles in one snapshot follows Poisson distribution with a mean number of mobiles provided as an input for the simulator.Hence,the number of mobile stations vary from snap shot to another,but over large number of statistically independent snap shots, the mean value is achieved.At the beginning of each snapshot,base stations’and mobile stations’powers are initialized to the level of thermal noise power.Thereafter,the path losses of coverage map are adjusted with mobile-dependent slow fading standard deviations.After this initialization,the transmit powers for each link between base station and mobile station are calculated iteratively in such a manner that E b/N0requirements for all connections are satisfied according to(1)and(4)for UL and DL,respectively.During a snapshot,a mobile performs a service connection establishment to a sector,which provides the best E c/N0on the CPICH:E c N0=p cpichP rx L k(9)where p cpich is the power of CPICH of the corresponding sector and P rx is the total received wideband power.A mobile is put to outage during a snapshot,if target E b/N0is not reached in either UL or DL,or the required E c/N0is not achieved in the DL.Also,the UL noise rise of a cell should not exceed the given 6dB limit during connection establishments5.The ratio between successful connection attempts and attempted connections during all snapshots is defined as service probability.After a successful service establishment,all other sectors are examined to see whether they satisfy the requirement to be in the active set(AS)of the mobile. If multiple E c/N0s from different sectors are within the soft handover(SHO)window,a SHO connection is established supposing that all criterion for a successful connection are achieved with all sectors in the AS.After each snapshot,statistics are gathered and a new snapshot is started.For every network configuration,at least 10000independent snapshots are taken.Presented results in the following section are averaged over all these snapshots.General simulation parameters are gathered in Table II.In most of the simulations,homogenous user distribution consisting of speech users is used.Afterwards,a part of the simulation scenarios is carried out5Cell noise rise is defined in(3).G ENERAL SIMULATION PARAMETERS.Parameter ValueBS TX P max[dBm]43Max.BS TX per connection[dBm]38BS noisefigure[dB]5CPICH TX power[dBm]33CCCH TX power[dBm]33SHO window[dB]4Outdoor/indoor STD for shadow fading[dB]8/12Building penetration loss[dB]15UL target noise rise limit[dB]6DL code orthogonality0.6Maximum active set size3TABLE IIIT RAFFIC AND MOBILE PROFILE CHARACTERISTICS FOR SPEECH,REAL TIME(RT)CIRCUIT-SWITCHED,AND NON-REAL TIME(NRT)PACKET-SWITCHED SERVICES.Parameter Speech RT NRTUL/DL bit rate[kbps]12.2/12.264/6464/128UL/DL E b/N0[dB]5/83/53/5Activity factor0.51-MS max.TX power[dBm]212424MS TX power dynamic range[dB]70Required E c/I0on CPICH[dB]-17by using a traffic mix of speech and data users with a nonuniform distribution.Table III introduces service type related parameters.V.S IMULATION R ESULTSA.Optimum Downtilt AnglesEvery site and antenna configuration is simulated with two different traffic volumes(referred to as low and high).The same downtilt angle is utilized for all antennas in the network(a network-wide downtilt angle). This approach targets in solving an expected average optimum downtilt angle for a certain site and antenna configuration.Note that the target is not to seek the same downtilt angle for a part of a network,but tofind an optimum downtilt angle depending on the site and antenna configuration.The definition of an optimum downtiltO PTIMUM DOWNTILT ANGLES FOR MECHANICALLY AND ELECTRICALLY DOWNTILTED ANTENNAS FOR ALL SIMULATED SITE AND ANTENNA CONFIGURATIONS.E VALUATION OF AN OPTIMUM DOWNTILT ANGLE IS BASED ON A SIMPLE ALGORITHM THAT UTILIZES INFORMATION OF RESULTING SERVICE PROBABILITIES WITH TWO DIFFERENT TRAFFIC VOLUMES.Site spacing Antenna height EDT EDT EDT MDT MDT MDT3-sec6◦3-sec12◦6-sec6◦3-sec6◦3-sec12◦6-sec6◦1.5km25m5.1◦7.3◦5.4◦5.7◦5.9◦4.9◦35m6.1◦9.1◦6.3◦7.3◦8.1◦5.9◦45m7.1◦10.3◦7.1◦8.1◦9.1◦7.0◦2.0km25m4.3◦5.6◦3.8◦5.1◦4.3◦3.8◦35m5.8◦7.9◦5.1◦6.7◦7.5◦4.8◦45m6.3◦9.3◦6.1◦6.9◦8.2◦5.9◦2.5km25m4.5◦5.2◦4.6◦5.1◦3.4◦3.7◦35m5.4◦7.6◦5.3◦6.1◦4.4◦4.5◦45m5.9◦8.3◦5.7◦6.9◦6.9◦5.8◦angle(ODA)is based on maximum service probability of low and high traffic volume scenarios.Hence,with an optimum downtilt angle,network coverage is guaranteed,and simultaneously,other-cell interference is mitigated as efficiently as possible.More detailed description of the definition method of ODA can be found from[15]. In the simulations,all downtilt angles are gradually increased in steps of2◦.Table IV gathers all optimum downtilt angles for all simulated network configurations.For all network configuration,ODAs increase as a function of antenna height and decrease as a function of site spacing. Generally,it can be also observed that the change of ODA from1.5km to2.0km site spacing than from 2.0km to2.5km site spacing,hence indicating that a small downtilt angle should be always used.Moreover, with12◦antennas,the required downtilt angles are expectedly higher than for6◦antennas.For the3-sectored configurations with6◦vertical beamwidth,the optimum downtilt angle varies between 4.3◦–8.1◦depending on the network configuration and downtilt scheme.According to(7)and(8),the corre-sponding downtilt angles would have been0.8◦–2.5◦and3.8◦–5.5◦.The simulation results indicate that an increase of the antenna height changes expectedly the optimum downtilt angle;10m increase in the antenna height corresponds roughly to1◦increase of the ODA.On the other hand,site spacing has comparatively smaller impact on ODAs,especially with larger site spacings.In the3-sectored configurations with12◦vertical beamwidth,the evaluated optimum downtilt angles range between3.5◦–10◦(Table IV).With definitions of(7) and(8),the downtilt angles would have been0.8◦–2.5◦and6.8◦–8.5◦,respectively.On average,the ODAs are intuitively higher for the12◦than for6◦beamwidth.However,the increase of ODAs is not as huge as one could expect.One reason for even lower ODAs for12◦beamwidth are the interference conditions that differ due to lower antenna gain and wider vertical spread of antenna pattern.Without any downtilt with6◦beamwidth, the signal power is more precisely directed towards the boresight,whereas antennas of12◦beamwidth provide(a)(b)Fig.3.(a)Service probability and(b)DL load for the3-sectored network configuration under high traffic volume.The network configuration consists of1.5km site spacing and25m antenna height together with either6◦or12◦vertical beamwidths.better coverage also in the areas closer to the base station in non-tilted scenarios.This results in lower other-cell interference levels,but on the contrary,prevents high capacity gains.An example plot of service probabilities and DL loads is given in Fig.3for the3-sectored network configurations with1.5km site spacing and25m antenna height under high traffic volume scenario.Moreover, curves are provided for both downtilt concepts and vertical beamwidths.Without any downtilt,the service probability is lower due to high level of other-cell interference that results in higher DL load as well.Moreover, higher level of other-cell interference can be clearly seen as lower service probability for vertically narrower antennas.Towards the optimum angle,DL load decreases due to reduction of other-cell interference and SHO overhead.On the other hand,in MDT,the DL load increases after certain downtilt angle due to increasing overhead of SfHO connections,which obviously limits ODA as well.However,the differences in ODAs between EDT and MDT are slightly different with these two vertical beamwidths.The reason for smaller ODAs for EDT network with6◦beamwidth is more efficient coverage reduction(see Section V.C).However,with12◦beamwidth the coverage reduction is not that efficient due to the wider vertical beam,but ODA is limited by the increase of SfHO connections.These phenomena depend heavily on the shape and width of the horizontal radiation pattern,and hence,e.g.,for horizontally90◦or120◦wide antennas,the relation between ODA for EDT and MDT might have been somewhat different.For6◦vertical beamwidth,the variations in service probability and DL load as a function of downtilt angle are higher within the simulated range,which makes the selection of downtilt angle also more sensitive with narrower antenna beamwidths.Thus,the results clearly indicate that antenna downtilt is not such critical for the sites equipped with vertically wide antennas,or in other words,the network capacity is not that sensitive to changes in the downtilt angle.However,it is reasonable to assume that downtilt of antenna with wider beamwidth becomes more important if the size of the dominance area becomes smaller like,e.g.,in urban areas.With6◦beamwidth,selection of downtilt angle between2◦–8◦would change the service probability with this particular traffic volume at maximum by3%.In EDT,the gain in service probability is limited by coverage,。

2024届高中英语阅读“阅”来越好1

2024届高中英语阅读“阅”来越好1

2023届高中英语一轮复习阅读精练1ClozeYou’ve been painting for a few years, and maybe you have even sold a painting or two. Are you ready to ___41___ the title of an amateur artist?Distinguishing green hand 菜鸟from professional artists is ___42___ task. It is not just a matter of your ability to create nice paintings. It’s not only about painting techniques. And for most cases, it doesn’t happen ___43___. V ery few artists become overnight success without years of struggle and suffering.To turn professional, people find it critical to develop a personal style. What makes your paintings ___44___ among other paintings out there? Are your paintings standing out unmistakably directed to you as the creator? A personal style comes along with technique, painting medium, and subject and it tends to develop gradually over time. You ___45___ it through unconscious and constant exploring and self-shaping. Style does not mean that you are painting the same subject or using the same painting medium. Salvador Dali used to use many artistic media, but they all have a ___46___ Dali style. Style refers to the emotions and thoughts delivered by your paintings, which people can identify with. Their ___47___ of the painter is then a sure thing.Artists talk about their ___48___ all of the time. What gets you out of bed every morning to paint? How do you find the energy to have all your time devoted to painting? ___49___, we all love to do what we do and we get a satisfaction out of creating. For the professional artist, it goes beyond that. Some artists wish to convey a deep message concerning life, society or even politics. Others simply seek ___50___ returns to cover kids’ tuition fees or pay family bills. Yet, all professional artists know that they have to keep working to achieve the goals.Many amateur artists passively wait for ___51___ to come. If they are not in the mood, they do not bother wasting the time. They sometimes allow themselves to be occupied by events like parties. Professionals are never easily ___52___ or torn away from their artwork in progress. Focused on their work so much, some even regard spending time outside their ___53___ as crime. ___54___ is their secret to high productivity.Besides, professional artists are constantly prepared to grab new ideas for the next painting, which they believe is sure to be better than the previous one. The belief that there is always room for ___55___ keeps driving them forward in the art world where many masters have come along.41. A. step beyond B. turn off C. see through D. make up42. A. rewarding B. tricky C. formal D. temporary43. A. individually B. thoroughly C. instantly D. sincerely44. A. unique B. superior C. practical D. reliable45. A. acquire B. transfer C. imitate D. analyze46. A. recent B. distinct C. modest D. logical47. A. preservation B. employment C. adaption D. recognition48. A. background B. significance C. motivation D. routine49. A. To sum up B. In contrast C. In addition D. In general50. A. academic B. global C. financial D. original51. A. inspiration B. fame C. guidance D. solution52. A. offended B. dominated C. distracted D. rewarded53. A. studio B. bedroom C. garage D. garden54. A. Reflection B. Devotion C. Creativity D. Illustration55. A. negotiation B. profit C. criticism D.improvement(B)Gustav MahlerBEWARE NUMBER NINEComposer Gustav Mahler (1860 – 1911) thought he could cheat death by not naming his ninth symphony by number. This was because several composers,including Beethoven and Schubert, had died after completing their ninthsymphonies. So Mahler called his ninth The Song ofthe Earth —and it worked, in a sense. He lived long enough to write most of histenth symphony, though he died before it was performed. Michael Jordan UNIFORMREDESIGNERMichael Jordan (1963– ) reportedly began the trendsetting change from mid-thigh basketball shorts to longer ones as a way of covering up a pair of University of North Carolina shorts, which hewore for good luck under his Chicago Bulls uniform. Charles DickensDREAM CATCHER Author Charles Dickens (1812– 1870) carried a navigational compasswith him at all timesand always faced northwhen he slept. He believed it improved his creativity and writing.④5. ____________ kept an irrational habit in order to improve their work. A. Benjamin Franklin and Gustav Mahler B. Benjamin Franklin and Charles Dickens C. Gustav Mahler and Charles Dickens D. Lucille Ball and Gustav Mahler6. Which of the following statements is TRUE ?A. A sharpened pencil was a necessity for John Steinbeck to improve his creativity.B. Gustav Mahler refused to finish his ninth symphony to avoid bad luck.C. Both Lucille Ball and John Wayne were afraid of certain stuff.D. Michael Jordan wore two pairs of basketball shorts in a match.7. Which of the following arrangements of the illustrations best fits the boxesLucille BallFEATHERED FOEOn the day that three-year-old Lucille Ball’s father died, a bird flew into her home and became trapped.Shocked by the events, she③developed a lifelong bird hatred. The actor (1911-1989)evenrefused to stay in hotels that had pictures of birds on the walls.numbered ①,②,③,④?a b c dA.d-b-a-cB. B. a-b-d-cC. d-c-a-bD. b-c-d-a(C)Delivering life-saving drugs directly to the brain in a safe and effective way is a challenge for medical providers. One key reason: the blood-brain barrier, which protects the brain from tissue-specific drug delivery. Methods such as an injection or a pill aren’t as precise or immediate as doctors might prefer, and ensuring delivery right to the brain often requires invasive, risky techniques.A team of engineers from Washington University in St. Louis has developed a new nanoparticle generation-delivery method that could someday vastly improve drug delivery to the brain, making it as simple as a sniff.“This would be a nanoparticle nasal spray, and the delivery system could allow medicine to reach the brain within 30 minutes to one hour,” said Ramesh Raliya, research scientist at the School of Engineering & Applied Science.“The blood-brain barrier protects the brain from foreign substances in the blood that may injure the brain,” Raliya said. “But when we need to deliver something there, getting through that barrier is difficult and invasive. Our non- invasive technique can deliver drugs via nanoparticles, so there’s less risk and better response times.”The novel approach is based on aerosol(气溶胶) science and engineering principles that allow the generation of monodisperse nanoparticles, which can deposit on upper regions of the nasal cavity via spread. The nanoparticles were tagged with markers, allowing the researchers to track their movement.Next, researchers exposed locusts’antenna( 触角) to the aerosol, and observed the nanoparticles travel from the antennas up through the olfactory nerve, which is used to sense the smell. Due to their tiny size, the nanoparticles passed through the brain-blood barrier, reaching the brain andspreading allover it in a matter of minutes.The team tested the concept in locusts because the blood-brain barriers in the insects and humans have similarities. “The shortest and possibly the easiest path to the brain is through your nose,” said Barani Raman, associate professor of biomedical engineering. “Your nose, the olfactory bulb and then olfactory cortex: two steps and you’ve reached the cortex.”To determine whether or not the foreign nanoparticles disrupted normal brain function, Saha examined the physiological response of olfactory neurons in the locusts before and after the nanoparticle delivery and found no noticeable change in the electrophysiological responses was detected.“This is only a beginning of a set of studies that can be performed to make nanoparticle-based drug delivery approaches more principled,” Raman said.The next phase of research involves fusing the gold nanoparticles with various medicines, and using ultrasound to target a more precise dose to specific areas of the brain, which would be especially beneficial in brain-tumor cases.8. This passage is mainly about ____________.A. a novel method of drug deliveryB. a challenge facing medical staffC. a new medicine treating brain diseasesD. a technique to improve doctors’ ability9. According to the passage, which of the following statements is TRUE?A. Doctors prefer using methods like an injection to treat diseases.非侵入性的治疗B. Locusts were tagged with markers to track their movement.C. The blood-brain barrier lowers the effectiveness of a pill.D. The medicine could reach the brain within half an hour.10. The researchers focused their study on locusts because ____________.A. human and locusts have similar structures that protect brain from foreignsubstancesB. the delivery process consists of the olfactory bulb and the olfactory cortexC. locusts have changeable electrophysiological responses to nanoparticlesD. The shortest and possibly the safest path to the brain is through human’snoses11. ____________ would most be interested in reading this passage.A. A lung cancer patient who needs operation immediatelyB. A college student who majors in medical technologyC. A senior doctor who is about to retireD. A high school teacher who is teaching biology答案ABCAA BDCDC ACABDBDC ACAB。

Array (Smart) Antennas Improve GSM Performance

Array (Smart) Antennas Improve GSM Performance

Array (Smart) Antennas Improve GSM Performance Cornelius A. D. Pahalson;Nuhu Habila;Hyat Markus Gaga【期刊名称】《International Journal of Communications, Network and System Sciences》【年(卷),期】2024(17)1【摘要】As wireless data applications over cellular networks become more widespread, the pressure to increase capacity will become even more intense. Capacity in the 800 and 900 MHz bands, where bandwidth is restricted, is already becoming a limiting factor. This paper attempts to address how the application of smart antenna systems has brought about improvements in call quality and increased capacity through reduced Interference in Mobile Communication. The smart antenna may be in a variety of ways to improve the performance of a communications system. Perhaps most importantly is its capability to cancel co-channel interference. It helps in improving the system performance by increasing the channel capacity, spectrum efficiency, extending range coverage, speech quality, enabling tighter reuse of frequencies within a cellular network and economically, feasible increased signal gain, greater, reduced multipath reflection. It has been argued that Smart antennas and the Algorithms to control them are vital to a high-capacity communication system development.【总页数】10页(P1-10)【作者】Cornelius A. D. Pahalson;Nuhu Habila;Hyat Markus Gaga【作者单位】Department of Science, School of Science and Technology, Plateau State Polytechnic, Barkin Ladi, Nigeria【正文语种】中文【中图分类】TN9【相关文献】1.OPTIMAL DESIGN OF SMART ANTENNA ARRAY2.Analysis of electrical performances of planar active phased array antennas with distorted array plane3.Review of Research Techniques to Improve System Performance of Smart Antenna4.An improved peak side lobe reduction method for linear array antenna for military applications5.An Optimized Design of Antenna Arrays for the Smart Antenna Systems因版权原因,仅展示原文概要,查看原文内容请购买。

GNSS双接收机抗欺骗技术(

GNSS双接收机抗欺骗技术(

GNSS 双接收机抗欺骗技术*肖岭,唐小妹,李柏渝,孙广富(国防科学技术大学 电子科学与工程学院,湖南 长沙 410073)摘要:欺骗干扰能使目标接收机得出错误的位置、时间结果,是GNSS 应用安全性的一个严重威胁。

文中提出了一种利用两个接收机伪距测量值单差的抗欺骗方法,真实卫星信号的来向是不同的,因此不同信号的伪距单差是相异的;而对于单天线的欺骗干扰源,所有信号的入射方向相同,故伪距单差是相同的。

文中利用方差分析技术推导了基于伪距单差的欺骗信号最优检测量,并分析了检测量的统计特性。

经分析接收机噪声、接收机基线长度和卫星个数等参数对检测性能的影响较大;在接收机噪声和卫星个数未知的情况下,可以通过增大接收机基线长度来提高检测性能。

仿真结果表明,当接收机间的基线长度为10m 时,0.01虚警概率下,欺骗信号的检测概率可达98%。

关键词:欺骗干扰;伪距单差;方差分析中图分类号:TN95 文献标志码:A 文章编号:A GNSS Anti-spoofing Technique Based on Dual-ReceiverXIAO Ling, TANG Xiaomei, LI Baiyu, SUN Guangfu(College of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China) Abstract: The spoofing interference can mislead target receiver in resulting wrong position and time, it is aserious threat to the security of GNSS applications. The paper proposed an anti-spoofing method using the pseudo-range single-differences. As authentic signals ’ incident directions are different, thus the pseudo-range single-differences of different signals are dissimilar. While the directions of spoofing signals coming from the spoofing source with single antenna are same, so pseudo-range single-differences of these signals are identical. Using analysis of variance technique, the paper has deduced the optimal spoofing detection variable based on the pseudo-range single-differences, and analyzed the statistical character of the decision variable. After analyzing, the parameters such as receiver noise, the receiver baseline, and satellite number have a large influence on the detection performance; as the receiver noise and satellite number are uncertain, we can improve detection performance by increasing the length of baseline. When the baseline is 10 meters long, the simulation results illustrated that if the false alarm rate is 0.01, the spoofing detecting probability is up to 98%.Keywords: Spoofing Interference; Pseudo-range Single-differences; Analysis of Variance*收稿日期:2015-09-07基金项目:国家自然科学基金资助项目(61403413)作者简介:肖岭(1986-),男,河南方城人,博士研究生,E-mail :xiaoling_nudt@ 孙广富(通信作者),男,教授,博士,博士生导师,E-mail :sunguangfu_nnc@当前,由GNSS 提供的位置、速度和时间(PVT: Position , Velocity and Time )服务深刻影响着人们的生活,广泛应用于车辆运输导航、飞机导航及着陆系统、电网时间同步、数字通信网络时间同步、银行及股票市场交易的时间同步、紧急救援、汽车租赁中的车辆定位等领域。

高速射频交换矩阵设计

高速射频交换矩阵设计
24 个单刀 16 掷开关级联 16 个单刀 24 掷开关来组成需
(2)
C SPNT =
∑ 2 = mn - 1
i
要的 24×16 开关矩阵。
串 联 PIN 二 极 管 的 插 入 损 耗 IL 和 隔 离 度 ISO 的 计
算公式为:
总单元个数为:
log ( mn - 1)
损较大,单级开关隔离度只有 40 dB 左右,要达到 80 dB
关使用数量;
Copyright©博看网 . All Rights Reserved.
70
2015 年第 38 卷
现代电子技术
(6)将微波开关矩阵设计为一个单独系统,对所有
开关以及微波开关矩阵输入/输出端口物理位置进行固
对来说较小;PIN 开关的功率容量较好,插损小、隔离度
n 掷开关彼此选择端口两两相连所构成的。通过分别控
及信号变换的门电路,这些低频电路又对泄漏的射频信
制输入/输出单刀开关可自由组合,n 个输入端口与 n 个
号起到了很大的衰减作用,一般为 40~50 dB,因此射频
对应 1 个输出端口,即同一时间有 n 路通道,只是通道
从开关速度指标看两种开关均可满足要求。但对射频
输入驻波比
miniaturization and integration of electronic equipments.
Keywords:communication system;single⁃pole multiple⁃throw switch;high⁃speed RF switching matrix;design scheme
设计和配置射频交换矩阵时,应充分考虑测试需求
信号的原始信息不失真地记录下来,利用各种数字信号
  1. 1、下载文档前请自行甄别文档内容的完整性,平台不提供额外的编辑、内容补充、找答案等附加服务。
  2. 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
  3. 3、如文档侵犯您的权益,请联系客服反馈,我们会尽快为您处理(人工客服工作时间:9:00-18:30)。

The Research of Smart Antenna Technique for McWiLL Broadband WirelessCommunication SystemDongsheng WangThe College of Mechanical and Power Engineering Henan PolytechnicUniversityJiaozuo, Henan Province, 454000, Chinaxhwds@Yanru ZhaoThe College of Mechanical and Power Engineering Henan PolytechnicUniversityJiaozuo, Henan Province, 454000, Chinayanruzhao@Abstract—Recently, the smart antenna has become a very promising technique for wireless communication, which could enhance the system capacity. The smart antenna technique plays important roles in improving the frequency spectrum utilization efficiency, eliminating the multi-access interference and increasing the system capacity. The principle of smart antenna, the adaptive processing algorithms and the adaptive beam-forming algorithms are analysed in this article. The performances of the smart antenna and the traditional antnna in McWiLL system are compared. The advantages of the smart antenna in the performance, the power consumption and the cost are discussed. The smart antenna plays important roles in improving the covering range, restraining the interference and increasing the system capacity.Keywords-the smart antenna; beam; McWiLL; adaptive algorithmI.I NTRODUCTIONWith the development of wireless communication techniques, the more precious is it for the frequency resource. The problems of wireless environment such as improving the spectrum efficiency, eliminating the multi-access interference, eliminating the co-channel interference and the multi-path fading are all resolved by smart antenna technique perfectly. With smart antenna technique, the multi-path interference of different directions and the co-channel interference can be restrained effectively, the transmit quality of signal and the spectrum efficiency can be increased and the system capacity can be enlarged [1].II.P RINCIPLE AND A RITHMETIC OF THE S MARTA NTENNA T ECHNIQUEA.Principle of the Smart Antenna TechniqueThe original name of the smart antenna is adaptive antenna array. The smart antenna technique bases on the principle of spatial signal superposition to make the wave beams superpose each other and then forms wave beams with certain direction in space [2, 3]. The smart antenna consists of two parts of both the radio frequency antenna array and the signal processing. The receiving and sending of the antenna array are controlled real time by the part of signal processing According to the communication information obtained.The array modes of the smart antenna can be divided into three kinds: the linear array, the circular array and the planar array. The interval between every two array elements is half of the wavelength. By adjusting the weighted amplitude and the phase of the array elements, the antenna direction pattern of the array can be changed and the users’ directions can be surveyed automatically and pointed to by the wave beams to make the wave beams move along with the users.B.Adaptive Processing AlgorithmsThe adaptive space tracking filtering mobile station is adopted in the smart antenna and the movement of the mobile station will cause the change of the wireless channel. The choice of weight vector is on the basis of the statistical characteristics of the array receiving signals. The beam formers are optimized according to the rules preestablished. The antenna direction pattern can be obtained by making some cost functions minimum in optimized beam formers. The optimized signals of the array fan-out can be got by making the cost functions minimum because the cost functions are inversely proportional to the signal quality of the array fan-out.Several optimization criteria of beam formers [4-7]:1)Minimum Mean Square Error Criterion:The minimum mean square error criterion is to make the mean square value of estimated error minimum, that is, the mean square error between the array output )()(tXWt y T= and the reference signal d(t) is minimum, namely:22)]()([))((tXWtdEtE T−=ε (1) Make the formula above expanded:RWWrWtdEtE TT+−=2)]([))((22ε (2) Where, r is the cross-correlation matrix and R the correlation matrix.)())((tXtdEr= (3))(HXXER= (4) Compute the gradient of the Weight vector and the gradient operator can be derived from the following equation.rRWtEW22)))(((2−=∇ε (5) If the gradient operator is zero, the optimization weight vector under the minimum mean square error criterion can be calculated as follows.2009 Second International Conference on Intelligent Computation Technology and Automationr R W opt 1−= (6)2) Maximum Signal Noise Ratio Principle: The maximum signal noise ratio principle is on the basis of the principle that the ratio of desired signal power to noise power is maximum.()H s R E ss = (7)()H u R E uu = (8)Where, s is the desired signal and u the noise.The output signal power can be computed as follows. 22(||)H H s s E W s W R W σ== (9) The output noise power can be computed as follows. 22(||)H H u u E W u W R W σ== (10) The output signal noise ratio can be calculated as follows.22H s s Hu u W R W SNR W R Wσσ== (11)The optimization weight vector that makes the output signal noise ratio maximum is the eigenvector correspondingto the maximum eigenvalue of the matrix 1u s R R −, that is,suppose max λis the maximum eigenvalue of the matrix 1u s R R − and the optimization weight vector can be derived from the following equation. 1max u s opt opt R R W W λ−= (12)The weight vectors of three principles are the special cases of Wiener solution, so the output characteristic of the array can not be influenced by different principles. The weight vectors can be obtained recursively with adaptive algorithms because the condition is variable continuously. It is of great importance to choose proper adaptive beam-forming algorithms because the convergence rate of algorithms and the complexity to carry out with hardware are decided by adaptive beam-forming algorithms. C. Several Typical Adaptive Beam-forming AlgorithmsThe adaptive algorithms are the core of the adaptivesmart antenna and decide the transient respondence speed ofthe antenna and the complexity of circuit. The spatial filtering and frequency filtering can be carried out via adjusting the gain weights of the antenna according to thealgorithms automatically. The adaptive algorithms can bedivided into two kinds, the non-blind algorithm and the blindalgorithm. The non-blind algorithm carries out adaptation byright of the reference signal. The blind algorithm makes the output accord with the characteristics by adjusting the weightwithout transmitting pilot signal and training sequence [8, 9]. 1) Non-blind Beam-forming Algorithms : Adopt inverse method to specimen correlation matrix(DMI):Suppose the received signal of array is x (k ) and the reference signal d (k ), the autocorrelation matrix R xx of x (k ) can be defined as follows in spatial statistics.[()()]H E k k =xx R x x (13)The cross-correlation vector r xd between x (k ) and d (k ) can be defined as follows.*[()()]d E k d k =x r x (14) The optimized weight of the typical wiener filter can be defined as follows.1d −=xx x w R r (15) Generally, R xx and r xd can not be calculated directly because the signal, the interference and the noise are unknown. The method bases on maximum-likelihood principle to estimate R xx and r xd with N sampling values of the observed signal.¦==N j T xx j x j x N R 1*)()(1ˆ(16)¦==N j xd j d j x N r1*)()(1ˆ (17) The weight can be computed as follows.xd xxr R w ˆˆ1−= (18) The inverse to specimen correlation matrix is adopted inthis algorithm and the computational complexity increases with the matrix order, so this algorithm is restricted in realapplications. Least mean square algorithm (LMS):The least mean square algorithm is on the basis of the principle of least mean square error and the gradientestimation steepest descent algorithm. The iterative refinement of the weight is on the basis of the weight gradient of the quadratic estimate and the movement of half step of the weight along the negative gradient direction. The constant deciding the size of every step is named the step size and the estimated weight will limitless near to theoptimal solution if the step size small enough. The error can be minimized with the stochastic gradient on condition that the reference signal d of the expected signalis known. ()()()()H e k d k W k X k =− (19) The iterative formula of the weight vector can be derived from the following equation. *(1)()()()W k W k X k e k μ+=+ (20) Recursive least squares algorithm (RLS): The recursive least squares algorithm is on the basis of the output square sum of every snapshot array minimum, i.e., the least square criterion.)()()1()(*k k u k w k w ε+−= (21) 1111()[(1)()()(1)]H k k k k k λ−−−=−−−xx xx xx R R u x R (22) Where()()(1)()H k d k k k ε=−−w x (23))()1()()()1()(11k x k R k x k x k R k u xx H xx −+−=−−λ (24) The matrix inverse operation with recurrence method isapplied in the recursive least squares algorithm. The problems of heavy computation and high complexity in the recursive least squares algorithm are settled to a certain extent, but the deep null steering can not be formed in the direction of the interference signal.2) Blind Beam-forming Algorithms: The blind beam-forming algorithm is mainly the constant modulus algorithm and its’ basic idea is that the constant modulus signal can bring disturbance amplitude to destroy the constant modulus characteristic of the signal when the constant modulus signal suffers multi-path fading, additive interference and other disadvantageous factors. The fluctuation of signal envelope becomes less and is likely to resume constant envelope on the receiving terminal of the constant modulus algorithm by adjusting the weight of antenna array.The cost function defined by the constant modulus algorithm can be expressed as follows.()||()||||p p qk J W E y k a ªº=−¬¼ (25)Where, a is the amplitude of the expected signal on the output terminal of the array and p and q is 1or 2, respectively. The optimal solution of the constant modulus algorithm can be approached gradually with an iterative method because the cost function is nonlinear. The constant modulus cost function can be optimized with the gradient descent algorithm. The steepest descent algorithm with different astringency and complexity can be got if p and q get different values.The iterative formula can be calculated as follows when p =1, q =2 and a =1.*(1)()()()k k k e k μ+=−w w x (26) ()()()H y k k k =x w (27)()()2(())()y k e k y k y k =− (28)The structure of the constant modulus algorithm is simple and its’ astringency is decided by the initial value and step factor set in advance. The step should be revised carefully because the convergence rate is slow with small step and the performance is maladjusted with large step.III. A PPLICATIONS OF THE S MART A NTENNA IN M C W I LLC OMMUNICATION S YSTEMS The capacity and service quality of the communication system can be improved with the smart antenna technique. The McWiLL broadband wireless communication system adopting the adaptive antenna array technique developed independently by Datang Telecom Group combines the smart antenna technique with TDD and synchronous CDMA technique to form particular technical advantage.A. Upgrade the Covering RangeFig. 1 shows the comparison on the performance, the power consumption and the cost between the traditional antenna and the smart antenna. There are three terminals in the system named terminal A, terminal B and terminal C, respectively. The base station sends signals to the three terminals when all of the three terminals are in communication state and the signals sent to the three terminals are named S A , S B and S C . The base station sends signals omnidirectionally in the covering range and all of the terminals will receive signals for the system with the traditional antenna [10]. In fact, omnidirectional signals sending will cause the waste of the radio frequency powerand bring serious interference.(a) (b)Fig. 1 The comparison between the traditional antenna and the smart antenna.(a) The traditional antenna; (b) The smart antennaThe smart antenna will work out the relevant characters of the channels according to the uplink signals received by every terminal and make uplink shaped-beam and downlink shaped-beam with the information so as to send and receive signals directionally for the system with the smart antenna. The signals S A , S B and S C can get to the relevant terminals of terminal A, terminal B and terminal C with strong gains and only little power leak to the irrelevant terminals. Not only a mass of the radio frequency power can be saved but also little interference brought to other terminals with the downlink shaped-beam of the smart antenna.The comparison of covering effects between the traditional antenna and the smart antenna with the same geographical position and communication environment are shown in Fig. 2.(a) (b)Fig. 2 The comparison of covering effects between the traditional antennaand the smart antenna with the same geographical position andcommunication environment. (a) Covering effects of the traditional antenna;(b) Covering effects of the smart antennaThe transmit power of the traditional omnidirectional antenna is 2W and the smart antenna adopts eight antennae,the transmit power of which is 2W. If the covering range of the traditional antenna is the same as the smart antenna, the transmit power of the traditional antenna should be increased in 64 folds, i.e. 128W. It will add the cost, the volume and the design difficulty of the base station which are caused with a lot of heat brought by the large power amplifier to increase the transmit power.B.Disturbance Restraint and Same Frequency GroupNetworkThe smart antenna technique has the strong ability of suppressing interference and makes the covering capacity improved largely. The interference restraint of the smart antenna among cells is shown in Fig. 3.(a) (b)Fig. 3 The interference restraint of the smart antenna among cells. (a) Theuplink; (b) The downlinkThe contributions to the interference restraint of the smart antenna can be divided into two aspects: one is the interference among users and cells reduced largely with space shaped-beam; the other is to bring received signal null steering in the direction of interference to restrain the interference signal with null steering technique. In McWiLL system, the interference restraint capacity of the null steering algorithms can reach 20-30dB. The null steering algorithms can be used to restrain the interference signals effectively both inside and outside of the system. The interference restraint capacity of the smart antenna can be used to improve the signal-to-noise ratio and signal-to-interference ration of the received signal.The interference null steering technique is used to restrain the co-frequency interference from the adjacent base station in McWiLL system. The operating frequency of the base station A is the same to that of the base station B and the channel of terminal T A is the same to that of terminal T B, as shown in Fig. 3. For uplink, the base station A brings the interference null steering aiming at the interference signal transmitted by the terminal and the base station B brings the interference null steering aiming at the interference signal transmitted by the terminal T A that can reduce the co-frequency interference from terminal T A to the base station B and from terminal T B to the base station A. The null steering technique can be used in both uplink and downlink with TDD mode and the downlink also can restrain the co-frequency interference. The group network mode with the frequency reuse coefficient N=1, 2 and 3 is shown in Fig. 4. The same frequency group network should show the best performance designed beforehand on condition that the frequency reuse coefficient N =1.Fig. 4 The group network mode of N=1, 2 and3IV.C ONCLUSIONAt present, the smart antenna technique has been paid great attention to in the communication industry. The TD-SCDMA system which is the international standard for the third generation of mobile telecommunication applies the smart antenna technique and has a good effort. With the improvement of the technology, the smart antenna technique will provide an advanced technology platform to promote the mobile communication development.A CKNOWLEDGMENTThis work was supported by Doctoral Foundation of Henan Polytechnic University.R EFERENCES[1]R. Han, R. Sun, “Analysis of the smart antenna technology in futuremobile communication systems,” Science & Technology Information, no. 33, pp. 86-87, November 2008.[2]M. Li, J. Chen, “The smart antenna technology in WiMAX system,”Shanxi Electronic Technology, no. 3, pp. 59-60, March 2008.[3]Z. Song, “Intelligent antenna technology and application in TD-SCDMA,” Journal of Chongqing University of Posts and Telecommunications (Natural Science), no. S1, pp. 36-38, June 2007.[4]R. Jin, J. Geng, Y. Fan, The smart antenna of wirelesscommunication, 1st ed., Beijing: Beijing University of Posts and Telecommunications Press, 2006, pp.95-142.[5]Y. Gong, Adaptive Filtering: Time Adaptive Filtering and the SmartAntenna, 2nd ed., Beijing: Publishing House of Electronics Industry, 2003, pp.22-68.[6] F. Lu, Y. Liu, X. Li, “Performance analysis of system simulation onone kind of compact TD-SCDMA smart antenna,” Telecom Engineering Technics and Standardization, no. 10, pp. 12-15, October 2008.[7]Y. Zhao, S. Yuan, Y. Wang, “Research on beam forming of smartantennas in the TD-SCDMA system,” Electronic Science and Technology, vol. 21, no. 11, pp. 5-8, February 2008.[8]R. Jin, J. Geng, Y. Fan, The smart antenna of wirelesscommunication, 1st ed., Beijing: Beijing University of Posts and Telecommunications Press, 2006, pp.159-179.[9]L. Ma, Smart Antennas for Wireless Communications: IS-95 andThird Generation CDMA Applications, 1st ed., Beijing: China Machine Press, 2002, pp.167-169.[10] B. Wen, B. Lin, Y. Liu, L. Jiang, X. Li, McWiLL Broadband WirelessAccess Technology and the application, the first ed., Beijing: Posts & Telecom Press, 2009, pp.38-47.。

相关文档
最新文档