Document No. ProductVersionConfidentialityV2.00Wireless Network System RadioFrequency Research DepartmentHuawei Technologi...
Revision RecordDate RevisedversionDescription Author1,999 1.00 Complete the first draft. Ai Ming2000/11/9 1.00 Transfer th...
Table of Contents1 Overview..................................................................................................
Basic Principles and Design Specifications ofAntenna in Mobile Communications(Second Edition)Key words: Mobile communicati...
1 Overview1.1 AntennaWith the rapid development of China’s economy, great changes have taken place inthe communications in...
小型化强度 Miniaturized strength 区域距离 Distance betweenregions衰落多路径 Fading multipath 机械结构 Mechanical structure电气指标 Electrical in...
1.2 Development Trends of BS AntennaBS antenna is the bridge between user terminal and the Base Station Controller(BSC). I...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001双极化天线 Bipolar antenna 主接收 Main receiving...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001The BS antenna is a kind of open field-e...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001The vehicle-mounted BS is usually used i...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001To determine the hardware technical spec...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001设计输出 Design output结构布局 Structure layout ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001If the system design should be based on ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001系统要求 System requirements 高电平均匀照射业务区 Even...
Basic Principles and Design Specifications of Antenna in Mobile Communications 0012.3 Types of AntennasThe structure or ty...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001Experiments show that beam downtilt can ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001天线 Antenna 低旁瓣 Lower side lobeD/U 值增加,上旁...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001基站天线 BS antenna 分集天线 Diversity antenna单个...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001Note 2: Bottom feed refers to the case t...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001偶极子 Dipole 馈电路 Feeder circuit几何机构 Geomet...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001www.TempusTelcosys.com
Basic Principles and Design Specifications of Antenna in Mobile Communications 001www.TempusTelcosys.com
Basic Principles and Design Specifications of Antenna in Mobile Communications 001Figure 12 HFSS simulation instanceThese ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 0012.4.2 Vertical Shaped-beam Antennaixed t...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001Figure 14 Pattern of antenna array with ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001the carrier on the boarder of the area i...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001In the mobile telecommunication, the sig...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001appropriate to have less than 0.7. In th...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001辐射方向图 Radiation pattern 90o方向 90oFigure ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001The following result can be obtained as ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 0012.6 Passive Inter-modulation of Base Sta...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001TX 产生 3 阶交调对 RX的干扰TX generates 3-orderin...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001Table 2-2 Table 2 Basic PIM suppression ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001P PAWhere, is the radiation power of ant...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001directional antenna, the included angle ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 0011)2)3)3.9 Upper Side Lobe SuppressionTo ...
Basic Principles and Design Specifications of Antenna in Mobile Communications 001双频双极化天线 Two-band dualpolarization antenn...
Basic Principles and Design Specifications of Antenna in Mobile Communications 0013.16 DimensionsTo facilitate the storage...
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Basic Principles and Design of The Antenna in Mobile Communications

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Basic Principles and Design of The Antenna in Mobile Communications

  1. 1. Document No. ProductVersionConfidentialityV2.00Wireless Network System RadioFrequency Research DepartmentHuawei Technologies Co., Ltd.Product Name: M900/1800 Total Pages: 37Basic Principles and DesignSpecifications of Antenna in MobileCommunications(Revised edition, for internal use only)Prepared by Ai Ming Date 2001/09/08Reviewed by Date yyyy/mm/ddReviewed by Date yyyy/mm/ddApproved by Date yyyy/mm/ddTempus Telcosys(P) Ltd.Time is Almighty.www.TempusTelcosys.com
  2. 2. Revision RecordDate RevisedversionDescription Author1,999 1.00 Complete the first draft. Ai Ming2000/11/9 1.00 Transfer the draft to the network planningtechnical support teamNetwork planning technicalsupport team2001/09/8 2.00 Revise the draft. Ai Ming♦ Note:1) The basic concepts of middle feed and bottom feeder of omni antenna are added; Sections 3.10 through3.13 are added2) Correct the errors in some figures. (2001-09-08)www.TempusTelcosys.com
  3. 3. Table of Contents1 Overview......................................................................................................................................... 51.1 Antennas............................................................................................................................... 51.2 Development Trends of BS Antenna .................................................................................... 71.3 Design Concepts of BS Antenna .......................................................................................... 82 Basic Technologies....................................................................................................................... 92.1 BTS Antenna......................................................................................................................... 92.2 System Requirements and Antenna Technologies ............................................................ 122.3 Types of Antennas.............................................................................................................. 152.4 Design of Shaped-beam Antenna....................................................................................... 192.4.1 Fan Beam Antenna .................................................................................................. 192.4.2 Vertical Shaped-beam Antenna ............................................................................... 242.4.3 Beam Tilt .................................................................................................................. 252.5 BS Diversity Antenna.......................................................................................................... 262.6 Passive Inter-modulation of Base Station Antenna ............................................................ 312.6.1 Relationship between PIM and Receiving-transmitting Frequency ......................... 312.6.2 PIM Generator and Suppression Technology.......................................................... 323 Major Index Requirement for BS Antenna Design................................................................... 333.1 VSWR of BS Antenna......................................................................................................... 333.2 Gain (dBi)............................................................................................................................ 333.3 Half Power Beam Width (HPBW) ....................................................................................... 343.4 Front-to-Back Ratio (F/B).................................................................................................... 353.5 Isolation between Ports ...................................................................................................... 353.6 Polarization ......................................................................................................................... 353.7 Power Capacity................................................................................................................... 353.8 Zero Stuffing ....................................................................................................................... 353.9 Upper Side Lobe Suppression............................................................................................ 363.10 Beam Downtilt................................................................................................................... 363.11 Two-band Dual Polarization Antenna ............................................................................... 363.12 Two-band Dual Polarization Duplex Antenna................................................................... 363.13 Grounding system............................................................................................................. 373.14 Antenna Input Connector.................................................................................................. 373.15 Passive Inter-Modulation (PIM) ........................................................................................ 373.16 Dimensions ....................................................................................................................... 383.17 Weight............................................................................................................................... 383.18 Wind Load......................................................................................................................... 383.19 Working Temperature....................................................................................................... 383.20 Humidity............................................................................................................................ 383.21 Lightning Protection .......................................................................................................... 383.22 3-Proof Capability ............................................................................................................. 38www.TempusTelcosys.com
  4. 4. Basic Principles and Design Specifications ofAntenna in Mobile Communications(Second Edition)Key words: Mobile communications, antenna gain, design specificationsAbstract: Base station antenna is a bridge between user terminal and the BaseStation Controller (BSC). It is widely applied in the cellular mobiletelecommunications and ETS wireless telecommunication systems. Thisdocument presents the history of antenna development, the basic antennatechnologies, and the major technical indices. Readers are expected to have anoverall understanding about the antenna of BSs in the mobiletelecommunications. The impacts of antenna lobe, antenna downtilt (mechanicaland electronic), isolation on the cell coverage and frequency reuse are alsomentioned in this document.Abbreviation List:Reference listName Author DocumentNo.Release date Available placeor channel forreferenceMobile Antenna System Manual Translated by Yang Kezhong and JinShuhua1997Cellular Mobile Telecommunications ---Design of BTS Antenna Feeder SystemXu Yubo 1998Mobile Telecommunications Engineering Lu Errui, Shun Rushi, etc.Microstrip Antenna Theory andEngineeringZhang Jun, Liu Kecheng, etc. 1998Cellular Mobile CommunicationEngineering DesignA. MarrolaTelecommunication Engineering DesignManual ---- Mobile TelecommunicationsBeijing Design Institute of Post andTelecommunications Departmentwww.TempusTelcosys.com
  5. 5. 1 Overview1.1 AntennaWith the rapid development of China’s economy, great changes have taken place inthe communications industry. Today, propelled by the technologies and the economicbenefits, communications industry has become one of the largest industries in China.Major telecommunication organizations are restructured to accommodate to the rapiddevelopment of this industry. Along with the advancement of communications industrytowards the information economy, communication is now become the key to thesustainable development of various sectors of economy.The development of the mobile telecommunication is even more remarkable.Nowadays, people are no longer contented to process the information flow in fixedplaces. Mobile telecommunications are in great demand when people are traveling oron vacation. In China, the significant change of mobile telecommunications is evident.Various types of mobile phones are everywhere bringing information about politics,economy, culture, and life to people. The largest GSM network in China now providesservices for its over 20 million subscribers. The wireless access development is alsowidely adopted to ensure the communications in rural and remote areas.New technologies and new devices in mobile communications posed as greatchallenges for antenna designers. For example, however small the terminal may be,user would not accept the idea if the conventional antenna is attached to his portablemobile terminal. Therefore, the antenna designers have to develop miniature or evenelectronic antennas to keep up with the development of modern technologies.In addition to small size, antenna designers have to seek more sophisticatedelements to equip the antenna with even more powerful functions such as thediversity receiving capability, optional polarity features, and capacity to reduce themulti-path fading. The focal point of antenna design is shifted from its physicalfeatures (e.g. small-size, light-weight, etc.) to sophisticated electromagnetic structure,so that antenna can play a significant role on the radio channel.Antenna design will involve the propagation features, local environments, systemcompositions and performance, Signal Noise Ratio (S/N), bandwidth features,antennas own mechanical structure, feasibility of production method, and theconvenience of installation. The type of the mobile communications also affects theantenna design. The antennas used for the terrestrial system, offshore system, airsystem, and satellite system differ a lot. In the cellular systems, the radiation patternshould conform to segmentation pattern to avoid interference. In the urban areas,diversity receiving function should be employed to offset the multipath fading.Antennas of smaller size are required for the terminal mobile. In the design ofportable devices (e.g. the mobile phone), the antenna and Radio Frequency (RF)front end circuit of transceiver should be integrated. Antenna unit and the equipmentshould be treated as an antenna system.In a word, the antenna should be designed as an organic party of the whole systeminstead of an independent part. See Figure 1.The design specifications described in this document only involve the base stationantenna (BS antenna) in wireless communication systems.www.TempusTelcosys.com
  6. 6. 小型化强度 Miniaturized strength 区域距离 Distance betweenregions衰落多路径 Fading multipath 机械结构 Mechanical structure电气指标 Electrical index 分集技术 Diversity technology人机界面 Man-machine interface 环境 Environment传播 Propagation 衰落 Fading干扰 Interference 人为故障 Man-induced failure天线 Antenna 系统 System频率复用 Frequency reuse 多信道连接 Multi-channel connection能力 Capability 类型 Type陆地 Terrestrial 海事 Marine航空 Navigation 卫星 Satellite个人化 CustomizationFigure 1 Integration of antenna and other systemswww.TempusTelcosys.com
  7. 7. 1.2 Development Trends of BS AntennaBS antenna is the bridge between user terminal and the Base Station Controller(BSC). It is widely applied in the cellular mobile telecommunications and ETSwireless telecommunication systems.The advancement of telecommunication technologies will definitely bring about theradical change of antenna. For the mobile communication system in1970s, the omniantennas or angle reflector antennas sufficed because the number of subscribers wasnot large. A few carriers and BSs can sufficiently cover a city and satisfy the demandsof mobile telecommunications in a city.However, mobile terminals are in great demand with the development of economy.Old BSs can no longer meet the demands. Moreover, new types of antennas arerequired as a result of the development of digital cellular technologies, so as toimprove the multipath fading, area planning and frequency reuse of the multi-channelnetworks. The flat type antenna was widely adopted in the GSM digital cellularsystem due to its features of low section, light structure, easy installation andoutstanding electronic performance.From the mid1980s to the late 1990s, the unipolar antenna was used. As threeantennas were needed for one sector (see Figure 2), and a cell was usually dividedinto three sectors, altogether nine antennas were needed for one cell. The largenumber of antennas brought great difficulties to the construction and installation of thebase station. Under such a circumstance, the duplex polarization antennatechnologies came into being. See Figure 3.单极化天线 Unipolar antenna 主接收 Main receiving发射 Transmitting 分集接收 Diversity receivingFigure 2 Configuration of unipolar antenna in one sectorwww.TempusTelcosys.com
  8. 8. Basic Principles and Design Specifications of Antenna in Mobile Communications 001双极化天线 Bipolar antenna 主接收 Main receiving发射 Transmitting 分集接收 Diversity receiving双工装置 Duplex deviceFigure 3 Two configurations of bipolar antenna in one sectorWith channels and new BSs added, the cellular network should be adjusted andoptimized, which demands new types of BS antennas such as adaptive antennas andintelligent antennas (The design specifications of these types will not be covered inthis document).1.3 Design Concepts of BS AntennaAs the number of mobile communication users is increasing, the frequency allocatedto the mobile communication has been gradually raised from 30MHz to 50MHz,150MHz, 250MHz, 450MHz, 800MHz and 1800MHz. The design of antennas hasalso been changed accordingly.The design of antennas primarily relies on some mathematical methods andComputer Aided Design (CAD). The up-to-date method is Finite Difference of TimeDomain (FDTD), which allows the radiation structure to be of any shape and to bemade up of multiple layers of different materials. The BS antennas are usually dividedinto directional antennas and omni antennas.The BS antennas used in High Frequency (HF) and Very High Frequency (VHF) andthe omni antennas used for Ultra High Frequency (UHF) are of the line-shaped type,which are usually analyzed and designed by the moments method. The directionalantennas used for UHF are normally the linear element antenna or paster-driven flattype antenna.These types of antennas can be analyzed and designed by using the element methodand Geometry Theory of Diffraction (GTD hybrid method). In fact, the latter type ofantennas can be simulated by the HFSS software of HP and Ansoft. HFSS can beused to easily obtain the electrical specifications of this type of antennas, and thenthe best design can be worked out.www.TempusTelcosys.com
  9. 9. Basic Principles and Design Specifications of Antenna in Mobile Communications 001The BS antenna is a kind of open field-effect radiator, which involves sophisticatedfield analysis and numerical analysis. However, pure and time-consuming theoreticalanalysis is not desired as antenna is intended for practical use. Designers shouldaccumulate experience and take the advantage of simulation software to work out theantenna design efficiently.As previously mentioned, the design of antenna should take the system compatibilityinto consideration. System design and antenna design are closely related. Acomponent (functional module) may be a high performance one when viewedindependently. However, it may not be the best choice from a system point of view.Take the printed paster antenna for example. It is less efficient than the commondipolar antenna. But due to its small cross section and the advantage of printingtechnology, it has helped turn a lot of new systems into reality. Its advantages areevident in the application of mobile telecommunication terminal, micro cellular, radar,and navigation equipment. Hence, antenna designer should especially take thefollowing factors into consideration:Regional structure: Determine the signal coverage area and the antennadirection.BS antenna: the antenna height, structure, installation, down tilt requirement ofbeams.Noise level: the thermal noise and ambient noise.Interference: the interference level, features, and co-channel interference andneighbor channel interference.Signal requirement: the best working frequency, bandwidth, cross interference,and frequency reuse.Cost of research, development, and processing.Reliability: the technical maintenance required, installation, and installationcharges.Vulnerability: Rust and corrosion if the antenna is installed outdoors.User requirementsThere are also some other factors that need to be considered.The key point is designers should turn these factors into specific requirements ofhardware design and then design the antenna according to these requirements.2 Basic Technologies2.1 BTS AntennaBS is widely used in the GSM digital cellular communication system, ETS wirelessaccess system and other terrestrial communication fields. For different fields, differenttypes of antennas are used, and the design specifications also differ.In the mobile communications, the BS serves the Mobile Station (MS). Generallyspeaking, it is fixed, though it also can be semi-fixed or vehicle-mounted. Thesemi-fixed BS refers to the BS whose location often changes, but communicationservice is not required when it is moving.www.TempusTelcosys.com
  10. 10. Basic Principles and Design Specifications of Antenna in Mobile Communications 001The vehicle-mounted BS is usually used in the vehicle dispatching center, whichrequires communication in mobile state. The document describes only the antennasof the fixed BSs.Figure 4 shows the major considerations in BS antenna design. Though the antennadesign belongs to electrical design in the narrow sense, it involves with many otherfields. The most important is hardware technological conditions worked out accordingto requirements of the system design.基站天线设计 BS antenna design 电气设计 Electrical design机械设计 Mechanical design 于无线链路有关的设计事项Design related to radiolink单元和天线件设计Unit and antennacomponent design区域特点 Regional feature要求的 D/U Required D/U 有无分集 Diversity requirement频率范围 Frequency range 单元 Unit方向图的合成 Pattern synthesis 馈电电路 Feeder cabling无源交调 Passiveinter-modulation风载荷设计 Wind load design地震负载设计 Earthquake design 天线罩设计 Antenna mask design结构件设计 Structure design 包装设计 Package designFigure 4 Key issues in BS antenna designwww.TempusTelcosys.com
  11. 11. Basic Principles and Design Specifications of Antenna in Mobile Communications 001To determine the hardware technical specifications, the electrical and mechanicalperformance should be compared, and tradeoff between performance and cost isnecessary. In some cases, performance and cost are put in the first place, followed bythe mechanical design of electricity. Figure 5 shows the procedures of antennadesign.基站天线设计方法BS antenna design 无线电链路预估Radio link estimation设备结构接口 Equipment interface 硬件分析 Hardware analysis成本预估 Cost estimation 分析数据 Analysis data测量数据 Measurement data 各种算法 AlgorithmsCAD 技术 CAM系统要求 System requirement 频率/带宽 Frequency/bandwidth信道/容量 Channel/capacity 业务范围 Service rangeD/U 值 D/U value 成本 Cost指标要求 Index requirement增益 Gain 方向图 Pattern极化特征 Polarization feature 机械性能 Mechanical feature尺寸/总量 Dimension/weightwww.TempusTelcosys.com
  12. 12. Basic Principles and Design Specifications of Antenna in Mobile Communications 001设计输出 Design output结构布局 Structure layout 天线效率 Antenna efficiency馈线网络 Feeder network 材料要求 Material requirement电气参数 Electrical parameters 机械参数 Mechanicalparameters成本组成 Cost compositionFigure 5 BS antenna design proceduresIn practice, it is of great importance to consider how to install the antenna after theantenna is assembled. It is because it may be much more expensive to install a BSantenna than to produce one. Therefore, not only production cost but also an antennastructure that allows easy installation should be taken into consideration.2.2 System Requirements and Antenna TechnologiesIn the mobile communication system, the antenna helps establish the wirelesstransmission connections between the wireless telephones. To ensure thecommunication between the BS and the MSs within the service area, the energy ofthe radio waves should radiate as evenly as possible, and the gain of the antennashould be as high as possible.As the width of the service area is definite, the gain cannot be raised by narrowing thehorizontal beam width. However, the vertical linear array antenna can raise theantenna gain effectively. In the cellular system, the gain of the BS antenna is usuallybetween 7 dBd and 15 dBd.Multi-channel communication is commonly used to increase the communicationcapacity and improve frequency reuse ratio. This requires a wide band system withfunctions of combiner and divider. At present, the frequency band of the BS devices inChina GSM cellular system is 890--960MHz. 890--915MHz is used for receivingsignals, and 935-960MHz for sending signals. The antenna relative band width isrequired to be greater than 8%, and intra-band VSWR less than 1.5. When theantenna is receiving and sending signals, passive inter-modulation will result, which inturn increases cross interference.With the rapid increase of the subscriber base, insufficiency of communicationchannels has become a problem for urban communications. To solve this problem,application of frequency reuse technology is strongly demanded. Though the cellularsystem can reuse frequency, the effectiveness of this technology relies on theradiation pattern of the BS antenna. The major-beam tilt and bean shapingtechnologies can improve the reuse of frequency effectively.Non-stadia transmission is one of the most common features in the mobilecommunications, especially in the modern cities. The numerous high buildings in thecity constitute a complicated radio transmission environment for the mobilesubscribers and result in fading of radio transmission. The receiving electrical level isthus affected and in some cases may fluctuate for more than 30 dB.www.TempusTelcosys.com
  13. 13. Basic Principles and Design Specifications of Antenna in Mobile Communications 001If the system design should be based on the lowest receiving level, the equipmentcould be rather expensive. The diversity receiving technology can overcome thefading effectively. Though application of this technology needs more devices, it is themost cost-effective solution from the system point of view and is at the moment themost commonly-used technology to overcome fading.Figure 6 shows the relationship between the system requirements and the antennatechnologies.www.TempusTelcosys.com
  14. 14. Basic Principles and Design Specifications of Antenna in Mobile Communications 001系统要求 System requirements 高电平均匀照射业务区 Even radiation of highlevel in the servicearea抑制业务区以外的辐射(频率复用技术)Suppression ofradiation outside theservice area(frequency reusetechnology)多信道宽频带 Multi-channel andwide frequency band稳定的接受电平 Steady receiving level 降低延迟扩展 Reduction of delayedexpansion体积小,重量轻,抗风 Compact, light, andwind-proof天线技术 Antenna technology主波束倾斜,赋形波束综合Integration of beamdowntilt andshaped-beamtechnologies宽带天线单元,宽带匹配网络Broadband antennaunit and broadbandmatching network分集接收 Diversity receiving 机械设计 Mechanical designFigure 6 System requirement and antenna technology2006-06-05 All rights reserved.www.TempusTelcosys.com
  15. 15. Basic Principles and Design Specifications of Antenna in Mobile Communications 0012.3 Types of AntennasThe structure or type of the BS antenna is determined by the size and landform of theservice area, and the number of cells and channels.If the service area is within the limited range of angles on the horizontal plane, theplat type antenna is often used. The half power beam angles of horizontal planeinclude 33°, 60°, 90°, 120°, 180°, etc.If the service area should be covered in all directions horizontally, the omni antenna isoften used, which can only tilted vertically. In the early cellular system, the length ofthe antenna was determined by the gain required, and even excitation was usuallyadopted for the array antennas to achieve a higher gain.Figure 7 is the diagram of the typical structure of the omni antenna.(a) Middle-feed mode (b) Bottom feed modeFigure 7 Omni antennaFor the middle-feed antenna (see note 1), if the beam downtilt technology is notapplied, the maximum directivity in the direction of 0° without any tilting or declining inthe whole working frequency band.As to the bottom-feed antenna (see note 2), however, the monotone phase variationof every unit will cause the maximum beam directivity to change with the frequency,which affects the network coverage seriously. When the cells should be re-divided toachieve the effective reuse of frequency, the value of D/U is a consideration moreimportant than antenna gain in BS antenna design. At present, the electrical ormechanical major-beam downtilt technology is commonly applied to the BS antennadesign in cellular mobile communications system.www.TempusTelcosys.com
  16. 16. Basic Principles and Design Specifications of Antenna in Mobile Communications 001Experiments show that beam downtilt can reduce the co-channel interference byabout 10dB, as shown in Figure 8. The network optimization experts have fullyrealized that the beam downtilt technology is the basic technology to increasefrequency reuse because it can form appropriate array antenna radiation pattern tocompress the side lobes beside the major beam, thus reducing the frequency reusedistance. Figure 9 shows how the BS antennas can be classified by functions and byfeatures.是理想的自由方向图假设条件下的Ideal pattern 计算方向图 Computed pattern接收信号强度 Strength of received signal 倾角=3oC Downtilt=3oC高基站距离 Distance between highBTSsFigure 8 Influence of beam downtilt to the frequency reusewww.TempusTelcosys.com
  17. 17. Basic Principles and Design Specifications of Antenna in Mobile Communications 001天线 Antenna 低旁瓣 Lower side lobeD/U 值增加,上旁瓣被抑制The D/U can beincreased to suppressthe upper side lobe.波束倾斜 Beam downtilt零点填充 Zero stuffing 高电平 High level业务区 Service area 干扰区 Interference areaFigure 9 Impact of side lobe on frequency reusewww.TempusTelcosys.com
  18. 18. Basic Principles and Design Specifications of Antenna in Mobile Communications 001基站天线 BS antenna 分集天线 Diversity antenna单个天线 Single antenna 阵天线 Array antenna单元天线 Unit antenna 水平面赋形波束 Shaped beam onhorizontal plane垂直面赋形波束 Shaped-beam onvertical plane空间分集 Space diversity极化分集 Polarization diversity 水平面波束控制 Beam control onhorizontal plane多波束 Multi-beam 均匀激励 Uniform excitement倾斜波束 E/M Beam downtilt E/M 旁瓣控制 Side lobe control零点填充 Zero stuffing 振子,微带贴片,寄生微带贴片Oscillator,micro-paster, parasiticmicro-paster微带,缝隙,角反射器天线Micro-strip, slot,corner-reflectorantennaFigure 10 Classification of BS antennaNote 1: Middle feeder refers to the case that the feeder point of the coaxial array omniantenna is at the middle element. In this case, no matter how the frequency changes,the phase change of the upper and lower elements is symmetrical, i.e., the maximumgain of antenna is at 0°(non-downtilt design technology).www.TempusTelcosys.com
  19. 19. Basic Principles and Design Specifications of Antenna in Mobile Communications 001Note 2: Bottom feed refers to the case that the feed point of the coaxial array omniantenna is at the bottom of each element(Bottom feed is different from the case that the power input point is at the bottom,because the power input point of the middle-feed antenna is also at the bottom. Thedifference between the middle-feed antenna and the bottom-feed antenna lies in theactual location of the feed point). In the case of bottom feed, the phase change fromthe lower to the upper elements is not symmetrical, i.e. the maximum directivity isrelated with the frequency.2.4 Design of Shaped-beam AntennaThe shaped-beam technology can increase the space frequency reuse rate. In thecellular system, the BS antenna is required to radiate the lowest possible level toanother cell using the same frequency, but the highest possible level to thepoorly-cover area within the service area. The shaped-beam antenna falls into twotypes. One is horizontal shaped-beam radiation pattern, referred to as fan beam inengineering; another is vertical shaped-beam radiation patter, or cosecant beam.In fact, the major-beam downtilt is not the shaped-beam technology in real sense,though they are used for similar purpose. This document only covers the design ofshaped-beam antenna in the cellular system. For implementation of beam synthesisand numerical technique, please refer to the related documents.2.4.1 Fan Beam AntennaIn the metropolitan cellular system, the horizontal beam of BS antenna is notomni-directional. The fan beam can effectively cover the service area and improve thereuse of frequency. The typical fan beam antenna is the corner-reflector antenna. Itcan adjust the beam width by controlling the angle of the reflector. Figure 11 showsthe basic geometry of the corner-reflector antenna.www.TempusTelcosys.com
  20. 20. Basic Principles and Design Specifications of Antenna in Mobile Communications 001偶极子 Dipole 馈电路 Feeder circuit几何机构 GeometricstructureH面方向图 Pattern onhorizontal planeFigure 11 Corner-reflector antennaIn the early cellular system, this type of antenna was commonly used to get the fanbeam. However, it is now seldom used due to its defects such as less compact feedernetwork, large cross section, and complicated structure. Hence, this document willdetail other types of fan beam antennas instead. These antennas are now commonlyapplied to the modern cellular system. See Figure 12-a, 12-b, and 12-c.www.TempusTelcosys.com
  21. 21. Basic Principles and Design Specifications of Antenna in Mobile Communications 001www.TempusTelcosys.com
  22. 22. Basic Principles and Design Specifications of Antenna in Mobile Communications 001www.TempusTelcosys.com
  23. 23. Basic Principles and Design Specifications of Antenna in Mobile Communications 001Figure 12 HFSS simulation instanceThese units are called plat antenna units due to their thin cross section. Whenassembled with the appropriate antenna cover, it looks like a flat board. The formulasused for the design of these antenna units are rather complex and the hybrid methodof MM and GTD is often resorted to. However, these methods are not suitable for anapplication engineer.To solve this problem, two American companies, Ansoft and HP, released the HighFrequency Simulation Software (HFSS) so that the answer to the electromagneticfield problem can be found out with basic antenna principles and experience aboutantenna on mind. Through the simulation of HFSS, flat antenna can change thevalues of width (W) and height (H) and thus can control the half-power beam width onthe horizontal plane.The half-wave dipole HFSS result can be controlled within the range of 55°-120° (Itcan be realized in terms of structure.). To obtain a beam width between 30° and 55°,two excitation sources should be placed in a certain interval on the horizontaldirection of the flat.Figure 13 is the HFSS simulation result of GSM 900MHz unipolar flat unit. Designersshould be noted that the effect of antenna cover on the radiation performance shouldbe taken into consideration.www.TempusTelcosys.com
  24. 24. Basic Principles and Design Specifications of Antenna in Mobile Communications 0012.4.2 Vertical Shaped-beam Antennaixed to a certain height covers a limited area ongnal level is equal in each spot of the serviceAs Figure 14 shows, the antenna fhorizontal plane so that the receiving siarea. To obtain shaped-beam on the vertical plane, multiple flat antennas are requiredto form an array on the vertical plane. Meanwhile, appropriate amplitude and phasefeeding are required for each unit. The amplitude and phase control technology offeeding network is very important for the beam shaping on vertical plane. The moreunits there are, the more ideal shaped-beam can be obtained.天线 Antenna 水平面 Horizontal plane低旁瓣区 e lobeLower sid 方向图 Pattern业务区半径 e nce areaRadius of servicarea干扰区 InterfereFigure 13 Shaped beam with low interference (vertical plane)www.TempusTelcosys.com
  25. 25. Basic Principles and Design Specifications of Antenna in Mobile Communications 001Figure 14 Pattern of antenna array with four antennas (horizontal)Figure 15 Pattern of antenna array with four antennas (vertical)HFSS can be firstly used to obtain the fan beam required. Its vertical pattern isFv( ).Take the four-unit array for example. The amplitudes and phases of the unitsnumbered from 1 to 4 are represented by A1, A2, A3, A4, ф1, ф2, ф3, and ф4respectively. The following equation can be obtained:f( ) = Ee−jkrr {A1e−jk( 32 dxCOS( )+ 1)+ A2e−jk( 12 dxCOS( )+ 2)+A3e−jk(− 12 dxCOS( )+ 3)+ A4e−jk(− 32 dxCOS( )+ 4)} Fv( )Change A1, A2, A3, A4, ф1, ф2, ф3, and ф4. With the help of computer, optimizationcan be done and the vertical shaped beam as shown in Figure 16 can be obtained.The figure clearly shows the first side lobe of the symmetrical radiation pattern ismuch higher.After the shaping, the upper side lobe is obviously suppressed and is improved by 7dB as compared with the symmetrical radiation pattern. The zero point of the lowerside lobe is stuffed and the radiation level in the service area is improved.2.4.3 Beam TiltThe beam tilt technology aims to tilt the major beam so that the level of the radiationtowards the frequency reuse area can be reduced. In this case, although the level ofwww.TempusTelcosys.com
  26. 26. Basic Principles and Design Specifications of Antenna in Mobile Communications 001the carrier on the boarder of the area is reduced, the interference level declines muchmore than the carrier level does. It is an advantage in the system design and isadopted worldwide by most of the cellular systems.Figure 16Figure (17-a) Maximum ratio combining of different correlation coefficients betweenchannelsThe beam tilt can also be realized through electric design. That is, the downtilt ofbeam can be achieved by adjusting the excitation coefficients, amplitude and phase.A set of antenna equipped with both electric downtilt and mechanic downtilt can beuseful especially during the network optimization when the fixed electric downtilt is farfrom enough.2.5 BS Diversity AntennaBS diversity antenna has been widely applied in the cellular systems. It can reducethe fading when the two antennas are two wave lengths away from each other onhorizontal plane. Although receiving diversity needs two or more ports, it caneffectively reduce the fading. As a result, the BTS power is reduced and thetransmission quality is improved.www.TempusTelcosys.com
  27. 27. Basic Principles and Design Specifications of Antenna in Mobile Communications 001In the mobile telecommunication, the signal received will be affected seriously inurban area with a lot of high buildings or forest with a lot trees. The fast fading iscaused by the reflection of fixed and mobile objects. Deep fading exists in a certainpart of the wave length.In a densely-populated area, the signals received by MS at any moment contain a lotof plane electromagnetic waves that are transmitted in parallel. The amplitudes,phases, and angles of these electromagnetic waves are random ones. Statistically,the amplitude and phase of one electromagnetic wave can be regarded asindependent of other electromagnetic wave. All the signal components aresynthesized into one complex standing wave, whose signal strength varies with thechange of each component.There could be a fading of 20-30dB in a distance of several vehicles and theexistence of large amount of propagation path results in the multi-path symptom. Thiskind of fading is not only found in the MS receive signal, but also BTS receive signal.However, the multi-path fast fading disappears in the place which is ten wave lengthsaway. That is, the diversity receiving can improve the communication reliabilitywithout increasing the transmitter power or channel bandwidth.The diversity receiving is based on one basic concept: when two or more samplingsare made for a random process, these samplings are fading independently. Theprobability that all the samples are less than a fixed value is much lower than theprobability that one sample is less than this value. Hence, the comprehensivesampling can help improve the performance of transceiver and the effect is muchbetter than the single sampling.The function of synthesis is to correct the phase and delay of signals after themulti-path transmission, add up the input signal level vectors, and add the noise atrandom. So the signal-to-noise ratio after synthesis of channels is generally greaterthan that of the single receiving channel. As the chance of simultaneous fading ofincoherent signals is slim, the system can be more reliable. Figure (17-b) shows howthe correlation coefficient changes with the height of the antenna and the distance.The structure of BS diversity antenna comes into three types: space diversity, patterndiversity, and polarity diversity. Space diversity is the most common one.Relationship between space diversity antenna and related coefficientsTo explain this relationship, one parameter is introduced, where =hbed ,hbe isthe effective height of the BS diversity receiving antenna and d is the distancebetween the BS diversity receiving antennas.Figure 17-b displays the curve that illustrates the relationship between coherent ofincidence angle ( ) and .In the urban area, as there are a lot of scatterers along the propagation path betweenMS and BS, the coherent is much smaller than that in the suburb. The greater thecoherent is, the higher diversity gain will be. When the coherent is greater than 0.7,the improvement of diversity gain is not so obvious than the case when is less than0.7.Figure 17-a shows that when the signal level is -10dB, the probability that theamplitude is lower than -10dB is 1.3% ( =0.7) or 0.52% ( =0.2). That is, when thecoherent drops from 0.7 to 0.2 and the probability is improved by 0.8% only. Whenboth the feasibility and cost are taken into consideration in practice, it is mostwww.TempusTelcosys.com
  28. 28. Basic Principles and Design Specifications of Antenna in Mobile Communications 001appropriate to have less than 0.7. In this way, the BSs in urban area will have abetter diversity gain.Figure 17-b also shows that when the receive signal reaches , the coherent isaffected substantially. When is equal to 0°, the coherent is the smallest and thediversity gain is the greatest. When is equal to 90°, the coherent is the greatest,while the diversity gain is the smallest. As the MS may move in any direction, i.e.,could be any value within the range of 0°~90°, and the antenna will not be designedbased on the best ( =0°) case or worst case ( =90°), it is recommended to adopt themean value 45° for and the distance between two receive antennas is determinedby =45° and =0.7.equaling to 45° and equaling to 0.7,With can be computed, i.e. 9. Table 1shows the effective heights and inter-antenna spaces of the diversity antenna.Table 2-1 Effective heights and inter-antenna spaces of the diversity antenna.( =45°, =0.7)Effective height ofdiversity antenna(m)20 50 70 80 90 100Space betweenantennas (m)≥3.0 5.6 6.7 7.8 8.9 10 11.1The following result can be obtained from the above data:d = 0.11hbe [M]The diversity gain is affected by the following factors: inter-antenna space, diversitycombination technology, diversity tuple, and communication probability. When theduplex space diversity and maximum ratio combination are used, the relationshipbetween diversity gain and coherent can be illustrated by Figure 17-a.For example, if the probability that the amplitude is larger than the horizontal ordinateis 90% and =0.7, the signal level is -4.6dB and the signal level of a single Rayleighchannel is -9.5dB. Thus, the gain of duplex space diversity is 4.9dB. The diversitygain corresponding to other probability can be obtained in the same way.When the antenna is placed horizontally as shown in Figure 17-c, its isolation isdetermined by the antenna radiation pattern, the space, and gain.www.TempusTelcosys.com
  29. 29. Basic Principles and Design Specifications of Antenna in Mobile Communications 001辐射方向图 Radiation pattern 90o方向 90oFigure 17 Horizontal placement of antennaGenerally, the fading introduced by Voltage Standing Wave Ratio (VSWR) is notincluded. If the gain of the transmit antenna on the maximum radio direction is Gat(dBi), the level of the side lobe at the direction of 90°is SLt, the gain of the receiveantenna on the maximum radio direction is Gar(dBi), the level of the side lobe at thedirection of 90° is SLr (dBp, against the major beam. The value is negative), thehorizontal spacing is Dh, the inter-antenna isolation can be given by:Adis = -22 - 20log (Dh/l) + (Gat + Gar) + (SLt + SLr) (dB) [negative]If the antenna is omni antenna, SLr=SLt=0 (dB) and l in the equation is the workingwave length. (regarded as far field). Generally the SL of 65° fan beam antenna isabout -18dBp, that of 90° fan beam antenna is about -9dBp, and that of 120° fanbeam antenna is about -7dBp. The actual value can be determined according to theantenna pattern.Example 1: 65° fan antenna, Gat=Gar=15dBi, SLt=SLr=-18dBp,f=915MHz,l=0.328mAdis=-30 dB (This index must be met in GSM system.)The following result can be obtained as per previous formula: Dh=1.25 l=0.41mExample 2: Omni antenna, Gat=Gar=11dBi,SLt=SLr=0dBp, f=915MHz, l=0.328mAdis=-30 dB (This index must be met in GSM system.)www.TempusTelcosys.com
  30. 30. Basic Principles and Design Specifications of Antenna in Mobile Communications 001The following result can be obtained as per previous formula: Dh=31.6 l=10.4mWhen the antenna is placed vertically, the isolation between two antenna isapproximately:Adis=-28-40log(Dv/l)垂直面内辐射方向图 Radiation pattern onvertical plane90o方向 90oFigure 18 Vertical placement of antennaFigure 18 shows the pattern space antenna for a whole cell. It is composed of foursets of antennas, forming an angle of 90° with one another. They are used to achievethe 180° fan bean in the omni pattern and are placed separately. The internalbetween two omni antennas is 0. Thus, the difference of antenna receive power iscaused by the difference of pattern.When the distance between the 180° fan beam antennas is 6 wave lengths, the testshows that the correlation coefficient is less than 0.2.Polarity diversity antenna emerges along with the rapid development of cellularsystem. It integrates two orthogonal (0°/90° or +45°/-45°) polarity antennas and thuscompactness is its most remarkable feature. However, the polarization feature ofincidence angle is more likely to be vertical polarization and the average receivepower of the port of 0°/90° dual polarization antenna differs a lot. Hence, theimprovement of Signal Noise Ratio (S/N) is less obvious than other diversitymeasures do. But with the +45°/-45° dual-polarization antenna, the diversity gainequivalent to the one of space diversity antenna can be obtained.2006-06-05 All rights reserved.www.TempusTelcosys.com
  31. 31. Basic Principles and Design Specifications of Antenna in Mobile Communications 0012.6 Passive Inter-modulation of Base Station AntennaPassive inter-modulation (PIM) is one of the major factors that generate co-channelinterference. When the antenna works in duplex mode, PIM should be considered. Inmost of the cases, the PIM on transmit channel is caused by the non-linear feature ofthe metal heterojunction that is found between the antenna radiation unit and thefeeder.The co-channel interference is thus generated on the receiving branch. To enablethe concurrent transmitting and receiving, the inter-modulation power should be lowerthan a standard value during the design and processing of antenna. For GSM cellularsystem, this standard value is around -103 dBm.2.6.1 Relationship between PIM and Receiving-transmitting FrequencySuppose the frequencies of two transmit carriers are respectively Fi and Fj, the (m +n)thmodulation is:mFi nfjF1M=Where, m and n are positive odd numbers and is the frequency of theinterference wave on the receiving band. The probability of the interference wave isdecided by the space between transmit power and receive power and the value of (m+ n).F 1MFor example, the transmit frequency of GSM 900 MHz cellular system in China fallswithin the range from 935MHz to 960MHz and the receive frequency from 890 to915MHz. The space between transmit power and receive power is 20MHz. Thus, thePIM is of 3-order. If no effective suppression measures are taken, serious interferencewill result. See Figure 19.2006-06-05 All rights reserved.www.TempusTelcosys.com
  32. 32. Basic Principles and Design Specifications of Antenna in Mobile Communications 001TX 产生 3 阶交调对 RX的干扰TX generates 3-orderinter-modulation thatinterferes RX.TX 产生 5 阶交调对 RX的干扰TX generates 5-orderinter-modulation thatinterferes RX.TX 产生 7 阶交调对 RX的干扰TX generates 7-orderinter-modulation thatinterferes RX.Figure 19 High-order inter-modulation and interferenceThe relationship between the order of PIM and the power generated can beapproximately illustrated by the formula: (m + n) × 10 dB. If the frequency spacebetween transmit wave and receive wave is small, 5-order or 3-order PIM willgenerate interference and the level will be higher than the 7-order PIM by 20 or 40dB.2.6.2 PIM Generator and Suppression TechnologyPower generated by PIM is determined by the metal type and the structure of theconnector. PIM is mainly generated on the antenna radiator, co-axial connector,welded joint and the contact surface that is likely to get rusted and corroded. By now,there is no definite answer to the relationship between PIM and the structure of thecontact point.With the rapid increase of mobile communication demand, a large number of BSantennas are in demand, especially the duplex antenna which is more cost-effective.The duplex antenna will be widely applied. Therefore, antenna designers shouldattach more and more importance to the development of PIM suppression technology.2006-06-05 All rights reserved.www.TempusTelcosys.com
  33. 33. Basic Principles and Design Specifications of Antenna in Mobile Communications 001Table 2-2 Table 2 Basic PIM suppression methodsPIM generator Suppression method:Radiator Use printed antenna to replace the oscillator unitConnector Increase the contact area and use silver plateWelded joint Reduce the number of welded joints and add solder to thewelded jointRust and corrosive surface Coat the surface to prevent the oxidationFeeding network Try to use strip line or micro-strip line to replace the cable3 Major Index Requirement for BS Antenna Design3.1 VSWR of BS AntennaFor the BS antenna of mobile communication cellular system, the maximum value ofVSWR should be less than or equal to 1.5:1. And this requirement should be met atthe specified working frequency band and temperature range. If the input impedanceof the antenna is ZA, the nominal characteristic impedance is , the reflectionfactor can be given by:Z0|Г| =|ZA−Z0||ZA+Z0|,VSWR =1+|Г|1−|Г|Where is equal to 50 . The matching feature of the port can also berepresented by the return loss:Z0R.L.(dB) = 20 |Г|logloglog .When VSWR is 1.5:1, the computed R.L. should be -13.98dB.3.2 Gain (dBi)The directivity characteristic of antenna can be depicted by the pattern. But generallythe value is used to show the concentration degree of the electromagnetic energyradiated by antenna, i.e. directivity factor D. D is defined by the following formula:D =SdS0|P∑d=P∑0When the thermal loss of the antenna is considered, the antenna efficiency Ashould be introduced. It is defined as follows:A =PPA2006-06-05 All rights reserved.www.TempusTelcosys.com
  34. 34. Basic Principles and Design Specifications of Antenna in Mobile Communications 001P PAWhere, is the radiation power of antenna and is the input power ofantenna.When the radiation performances of the two antennas are compared, if their inputpowers remain unchanged, the antenna gain can be given by:G = A×DG = 10 ((suppose the efficiency of unipole antenna is 100%).As generally the gain is given in decibel (dB), the gain can also be given bylogloglog A×D) dBi (as compared with Isotropic antenna).If the half-wave dipole is used as the reference antenna, the unit of gain is dBd and 0dBd equals to 2.15 dBi (see Figure 20). Other units will not be used for the BSantenna. Please note that the BS antenna gain refers to the gain of the workingfrequency band unless otherwise specified.实际天线 Actual antenna 半波偶极子天线 Half-wave dipoleantenna各向同性天线 Various likeantennasFigure 20 Relationship between dBi, dBd, ERP, and EIRP3.3 Half Power Beam Width (HPBW)As the BS antenna is generally erected vertically to the ground, the HPBWs of verticalplane and horizontal plane are often used to describe the HPBW of BS antenna. Therange of HPBW should be given for the working frequency band, e.g. 65°±6°.For a2006-06-05 All rights reserved.www.TempusTelcosys.com
  35. 35. Basic Principles and Design Specifications of Antenna in Mobile Communications 001directional antenna, the included angle between the two half-power points relative tothe maximum radiant point is the half-power beam width.3.4 Front-to-Back Ratio (F/B)Front-to-Back Ratio (F/B) is an important factor measuring the suppression ability ofthe antenna backward beam. It is the level difference between the maximum beamand the side lobe within the range of 180°± 30° starting from 0o. It is a positive valuein dB. F/B is associated with the antenna gain and the type of antenna and rangesfrom 18 to 45 dB.The specific index requirement is determined by the network planning andoptimization. At present, the F/B ratio of Huawei 900/1800 MHz directional antenna is20-25dB.3.5 Isolation between PortsThere are various types of multi-port antennas, such as dual polarization antenna,two-band dual polarization antenna, two-band dual polarization duplex antenna.When they work in duplex mode, the isolation between ports should be greater than30dB.3.6 PolarizationPolarization refers to the orientation of electric filed vector radiated by the antenna onthe space. The linear polarization antenna is often adopted for the BS.With the ground as the reference plane, if the electric field vector is vertical to theground, it is called Vertical Polarization (VP).If the electric field vector is parallel to the ground, it is called Horizontal Polarization(HP). The dual polarization antenna often adopts the +45° and -45° cross dual-linepolarization.3.7 Power CapacityPower capacity here refers to the average power capacity. Antenna is composed ofmatching device, balancing device, phase-shifting device, and other coupling device.The power it can bear is limited. Based on the actual maximum input power of BSantenna (Single carrier power is 20W.), if one antenna port can receive maximum 6carriers, the antenna input power should be 120W. Thus the power capacity perantenna port should be greater than 200W when the temperature is 65°C.3.8 Zero StuffingWhen shaped-beam design is adopted in the vertical surface of base stationantennas, the first zero point of the lower side lobe need to be stuffed without anyobvious depth, so as to make the radiant level more even within the service area.Usually, if the zero depth is greater than -26dB in relation to major beam, this meansthe antenna has zero stuffing.2006-06-05 All rights reserved.www.TempusTelcosys.com
  36. 36. Basic Principles and Design Specifications of Antenna in Mobile Communications 0011)2)3)3.9 Upper Side Lobe SuppressionTo enhance the frequency reuse efficiency and reduce the co-channel interference toadjacent cells in a microcell cellular system, the base station antenna beam can beshaped based on some principles.That is, those side lobes that aim at the interference area should be lowered as muchas possible, and the D/U value (ratio of strengths of desired and undesired signals)should be increased, and the level of the upper side lobe should be less than -18dB.There is no such a requirement for macrocell base station antennas3.10 Beam DowntiltAntenna downtilt needs to be adjusted to meet the coverage requirement or networkoptimization requirement. However, if the downtilt is adjusted mechanically, when thedowntilt is adjusted by an angle of more than 8°, the horizontal beam width of basestation antenna will loss its shape, which affects the sector coverage. At present,there are following types of beam downtilts:Fixed beam electronic downtilt. By adjusting the amplitude and phase of radiator,the antenna major beam can deviate from the normal direction of the antennaarray element for a certain angle, e.g. 3°, 6°, or 9°. When used together withmechanical downtilt, electronic downtilt allows an adjustable range of antennadowntilt angle of 18-20°.Manual-adjustable beam electronic downtilt. The adjustable phase-shifter can beadopted for the BS antenna, so that the direction of the main bean can beadjusted continuously within the range of 0-10° (not including the mechanicaladjustment).The major suppliers of this type of antenna includeHUBER-SUNNER and ALLEN DB.Remote-control beam electronic plunge angle. This type of base station antennais equipped with micro servo system. The phase shifter can be controlled by theprecision electric engine so as to remotely control the program. However, theaddition of active control circuit degrades the reliability of antenna andcomplicates the lightening-proof problem. DELTEC (New Zealand) is one of themajor suppliers of this type of antenna.3.11 Two-band Dual Polarization AntennaIt is a new type of antenna that integrates the antennas of two bands, e.g., GSM/DCS,GSM/WCDMA and DCS/WCDMA. See figure 21.3.12 Two-band Dual Polarization Duplex AntennaTo reduce the feeders, duplexer (in fact it is a filter combiner) is used to combine thetwo powers with the same polarization but different frequency into one. See Figure21.2006-06-05 All rights reserved.www.TempusTelcosys.com
  37. 37. Basic Principles and Design Specifications of Antenna in Mobile Communications 001双频双极化天线 Two-band dualpolarization antenna双频双工双极化天线 Two-band dualpolarization duplexantennaGSM 天线单元 GSM antenna unit DCS 天线单元 DCS antenna unit滤波合路器 Filtering combinerFigure 21 Multi-port antenna3.13 Grounding systemBS antenna is normally installed on a high position. To prevent the lightning strike, theDC resistance between inner and outer conductors of antenna port should bedesigned as 0.3.14 Antenna Input ConnectorTo reduce the passive inter-modulation and ensure the RF connection, the inputconnector of antenna adopts 7/16DIN-Female. Before the antenna is used, theconnector should be properly capped to avoid the oxidation and the intrusion ofimpurities.3.15 Passive Inter-Modulation (PIM)To reduce the noise resulting from the non-linearity of antenna, the PIM of antennashould be less than -103dBm (2x10W).2006-06-05 All rights reserved.www.TempusTelcosys.com
  38. 38. Basic Principles and Design Specifications of Antenna in Mobile Communications 0013.16 DimensionsTo facilitate the storage, transportation, installation, and ensure the security, so far asthe electrical indices are satisfied, the size of antenna should be as small as possible.3.17 WeightTo facilitate the storage, transportation, installation, and ensure the security, so far asthe electrical indices are satisfied, the antenna should be as light as possible.3.18 Wind LoadAs BS antennas are usually installed on high buildings and towers, it is required thatan antenna should work normally when the wind speed is 36m/s, and remainundamaged when it is 55m/s, especially in coastal areas where the wind is usuallystrong.3.19 Working TemperatureA BS antenna should work normally when the environmental temperatures is between-40°C and +65°C.3.20 HumidityA BS antenna should work normally when the environmental relative humidity isbetween 0 and 98%.3.21 Lightning ProtectionDirect DC grounding is required for all the radio frequency input ports of a BSantenna.3.22 3-Proof CapabilityA base station antenna should have a 3-proof capability, namely, humidity-proof, saltfog-proof and mould-proof. A base station omni-antenna should allow upside-downinstallation, and should satisfy the 3-proof requirement as well.2006-06-05 All rights reserved.www.TempusTelcosys.com

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