蓝牙与其射频技术

1、蓝牙及其射频技术1概述蓝牙作为一种新的短距离无线通信技术标准，具有普遍的应用前景，正受 到全世界各界的普遍关注。蓝牙技术有以下特点：支持用户在许多设备之间进 行无线数据互换及文件同步，使移动电话、便携式计算机和各类便携式通信设 备之间在近距离内资源共享；支持非可视范围内的通信与链接，且能在移动中 进行无线连接和通信；支持无线设备到有线网络之间的无线链接，只要连接到 局域网的蓝牙接入点，就可以够实现有线局域网的无线数据连接；支持电路互 换与分组互换，支持语音、数据和视频信号传输。它的应用几乎可以渗透到所 有通信及信息领域，具有极为普遍的应用前景。2蓝牙技术概况蓝牙的起源蓝牙的名字来源于10世纪丹

2、麦国王Harald Blatand，因为他十分喜欢吃蓝梅， 所以牙齿每天都带着蓝色。蓝牙将当时的瑞典、芬兰与丹麦都统一了起来。1999年12月1日，蓝牙特殊利益集团Bluetooth SIG发布了蓝牙技术最新 标准版。发展至今，加盟的公司已超过2000多家。一项公开的全世界统一的技术 规范能取得界如此普遍的关注和支持是前所未有的。固然，这主要得益于蓝牙 技术本身所具有的广漠应用前景和诱人的商机。蓝牙技术的特点蓝牙技术使用高速跳频和时分多址等先进技术，在近距离内最廉价地将几 台数字化设备呈网状链接起来。蓝牙是一个开放性的、短距离无线通信技术标准。它可以用来在较短距离 内取代目前多种线缆连接方案，

3、穿透墙壁等障碍，通过统一的短距离无线链路， 在各种数字设备之间实现灵活、安全、低成本、小功耗的话音和数据通信。蓝牙作为一种新兴的短距离无线通信技术已经在各个领域得到广泛应用， 它提供低成本、低功耗、近距离的无线通信，构成固定与移动设备通信环境中 的个人，使得近距离内各种信息设备能够实现无缝资源共享。蓝牙系统的参数指标及组成2.2.1蓝牙系统结构大体系统参数及指标工作频段：ISM频段一双工方式：TDD业务类别：同时支持电路交换及分组交换业务数据标称速率：1Mbit/s异步信道速率：非对称连接s s对称连接：s （全双工模式）同步信道速率：64kbit/s （3个全双工信道）信道间隔：1MHz信道

4、数：79发射功率及覆盖：0dBm（1mW），110m覆盖，20dBm（100mW），扩展至100m 覆盖跳频频点数：79个频点/MHz（2402+k）MHz，（k=0，1，278）；跳频速率：1600次/s数据连接方式：面向连接业务SCO（话音，电路交换、预留时隙）、无连接业 ACL（分组数据、分组交换、轮询）纠错方式：1/3FEC（3bit重复码），2/3FEC（截短Hamming码），CRC16, ARQ 密钥：以8bits为单位增减，最长128bits话音编码方式：CVSD或对数PCM网络拓扑结构：Ad hoc（无中心自组织）结构。蓝牙系统的组成蓝牙系统由无线单元、链路控制单元、链路管理

5、和软件结构和协议体系组 成。无线单元蓝牙天线属于微带天线，空中接口是成立在天线电平为0dBm基础 上的，遵从美国联邦通信委员会有关0dBm电平的ISM频段的标准。链路控制单元链路控制单元（即基带）描述了硬件基带链路控制器的 数字信号处置规范。链路管理器链路管理器（LM）软件模块设计了链路的数据设置、鉴权、链路 硬件配置和其它一些协议。软件结构和协议体系蓝牙设备应具有互操作性，即任何蓝牙设备之间都应 能够实现互通互连，这包括硬件和软件。设计协议和协议栈的主要原则是尽可能地利用现有各种高层协议，保证现 有协议与蓝牙技术的融合以及各种应用之间的互通性；充分利用兼容蓝牙技术 规范的软硬件系统和蓝牙技术

6、规范的开放性，便于开发新的应用。具体的协议 按SIG的需要分为4层：核心协、RFCOMM电缆替代协议、TCS电话控制协议以 及与Internet相关的高层协议3蓝牙射频技术蓝牙无线技术采用的是一种扩展窄带信号频谱的数字编码技术，通过编码运算增加了发送比特的数量，扩大了利用的带宽。蓝牙利用跳频方式来扩展频 谱。跳顿扩频是发射机以一个特定的与伪随机码序列一致的跳变速牢使信号从 一个频率跳到另一个，只有匹配的接收机知道发射机的跳频方式，可以正确地 解扩接收的数据。跳频扩频使得带宽上信号的功率谱密度降低，从而大大提高 了系统抗电磁干扰、串话干扰的能力，使得蓝牙的无线数据传输加倍靠得住。3. 1蓝牙的频

7、带和信道分派蓝牙系统一般工作在2. 4 GHz的ISM频段。起始频率为2. 402 GHz,终止 频率为2. 480 GHz,还在低端设置了2 MHz的保护频段，高端设置了3. 5 MHz 的保护频段。信道分派为厂一(2 402+k)MHz，其中k一0, , 78,共79个信道， 79个跳几回点。最大的跳频速度为1 660跳/秒。信道距离为1MHz。共享一个公 共信道的所有蓝牙单元形成一个微网，每一个微网最多可以有8个蓝牙单元，在 微网中，同一信道的各单元的时钟和跳频均维持同步。3. 2蓝牙射频收发技术特性蓝牙采历时分双工传输方案，利用一个天线利用不同的时间距离发送和接 收信号，且在发送和接收

8、信息中通过不断改变传输方向来共用一个信道，实现 全双工传输。蓝牙采用高斯移频键控(GFSK)以二进制的格式来传输数据，用正 频偏代表二进制，负频偏代表二进制0。蓝牙发射功率分可为3个级别：100 mw, 2. 5 mw和1 mw。一般采用的发送 功率为1mw,无线通信距离为10 m,数据传输速度达1 Mb/s。若采用新的蓝牙 2. 0标准，发送功率为100 mw,可使蓝牙的通信距离达100m,数据传输速度也 达到10 Mb/s。蓝牙接收机的实际灵敏度能达到一70 dBm。蓝牙利用接收机信号强度指示即RSSI（接收信号场强指示）功能进行功率控制，限定蓝牙设备的发射功率，以优化功耗和总的干扰电平。

9、当一个蓝牙设备检测到接收信号的强度时，他就返回信息以指示功率应该增加仍是减少。若是RSSI（接收信号场强指示）的值 与预期值相差太远，该蓝牙设备可以向另一设备请求调整输出功率。除此之外，蓝牙标准还对收发进程的寄生辐射、射频容限、干扰和带外抑 制等做了详尽的规定，以保证数据传输的安全。4蓝牙射频模块蓝牙无线技术利用串行通信，蓝牙无线设备实现串行通信是通过无线射频 链接，利用蓝牙模块实现。蓝牙模块主要由无线收发单元、链路控制单元和链 路管理及主机I/ O这3个单元组成，通常集成为1个或2个蓝牙模块，如图1所示。图1蓝牙模块的组成就蓝牙射频模块来讲，为了在提高收发性能的同时减小器件的体积和本钱， 各

10、公司都采用了自己特有的一些技术，从而使蓝牙射频模块的结构都不尽相同。 但就其大体原理来讲，蓝牙射频模块结构一般如下（参考爱立信）。图2蓝牙射频模块框图如图2所示，蓝牙射频模块一般由3个子模块组成：接收模块、发送模块和 合成器。各部份的主要功能如下：接收模块当射频模块在接收模式下时，信号由天线接收，通过滤波器 和收发控制开关进入接收模块。接收模块首先通过巴伦将从收发控制模块传来 的不平衡信号转为平衡信号(这样可以取得较高的共模抑制比)；然后通过一个 低噪放大器将接收的微弱信号放大，最后在解调电路中与从合成器提供的本振 信号作用，将载波信号解调输出。发送模块当射频模块在发送模式下，数据由基带模块输

11、入，在合成器 中进行载波调制，调制后的信号进入发送模块。在发送模块中，收发控制线选 通低噪放大器，将调制信号放大，并由巴伦转为非平衡信号输出至收发控制开 关。再由收发控制线选通至滤波器，通过天线向外发送。合成器合成器是收发模块中最关键的部份。合成器在频道选择和接收 模式时采用锁相环技术。在接收模式下，锁相环路闭合，用于提供接收模块解 调信号所需稳定的本振。在发送模式下，锁相环路开路，调制信号直接加载到 VCO上对载波进行调制。此时载波频率由环路滤波器输出电压维持。通常合成器 的工作频率仅为发射频率的一半，以减少与射频放大器的耦合。除此之外，通常蓝牙射频模块外接RSSI(接收信号场强指示)模块。

12、他将信 号反馈至解调电路，最终发送至基带处置芯片，以便按如实际接收状况调整信 号发射机的发送功率保障通信质量。目前蓝牙模块的具体实现有2种形式：双芯片结构和单芯片结构。双芯片结构由2块芯片组成：蓝牙收发模块（此模块将频率综合器、接收器 和发送器、中频滤波器等集成为一体）；蓝牙基带控制模块（将基带蓝牙处置器、 链路管理及微控制器集为一身，有的还集成Flash存储器）。这种模块技术成熟， 在市场上占主流。Philips公司推出的双芯片蓝牙模块就是由 BlueberryPCD87750基带控制器和BGB100射频收发器组成；爱立信蓝牙模块ROK101007由射频模块PBA313系列和基带控制器组成；

13、 Ateml公司的提供的AT76C55X单片Bluetooth控制器和T2901单片Bluetooth收 发器；朗讯科技的W7400底层模块和W7020射频模块等。单芯片结构的蓝牙器件将基频处置电路、RF电路（包括功率放大器和低噪音 放大器等）、微控制器、Flash E。PROM等集成到单个芯片中。这种模块起步较 晚，但近2年来发展迅速。如CSR公司的BlueCore系列蓝牙芯片；瑞士 XEMICS的 XE1400系列蓝牙芯片；法国Alcatel Microelectronics等公司在ISSCC2001上发 表了用于Bluetooth的单芯片ISI； Murata电子公司也宣称推出迄今为止最

14、小的 蓝牙模块。总的说来单芯片结构与双芯片结构各有优势。单芯片结构蓝牙模块 更“简化”便于利用，而且还有利于减小体积、功耗和本钱，有利于蓝牙集成 在其他设备如电话、PDA等小型移动设备中；双芯片结构技术成熟，在市场上占 主流。他将RF器件和基带部份相分离，就可使各公司发挥其所长。通过标准接 口，用户可以按照具体需要自行选择搭配基带和射频器件。这将使蓝牙芯片具 有更大的适应性和发展空间，充分发挥蓝牙技术的开放性。作为用户，应该按 照自己系统的实际要求选择单芯片结构仍是双芯片结构的蓝牙模块来实现自己 的系统。5结束语蓝牙作为一项新兴的技术。已从萌芽期进入了发展期，虽然有关蓝牙技术 本身、蓝牙技术和

15、其他短距离无线技术相较（如：IEEE 802. 1lb，HomeRF，IrDA） 的优势还存在很大的争议。可是，趋于成熟的蓝牙产品进入市场已是必然的趋 势。稍稍关注一下网络高科技市场，就会发现蓝牙技术从诞生的那一天起，就 一直被人们寄与了极高的期望。相信随着科技的进一步，蓝牙技术必将取得加 倍普遍的应用。参考文献沈连丰，宋铁成，刘云.通信新技术及其实验M.北京：科学出版社，2003金纯，许光辰，孙睿.蓝牙技术M.北京：电子工业出版社，2001马勒，Nathan Muller J.蓝牙揭密M.北京：人民邮电出版社，2001通信新技术及其实验结课论文蓝牙及其射频技术系 别：电子信息系专 业：通信工

16、程班级学号：4070709姓 名：曾庆东指导教师：高军时 间： 2010/6/162010/6/23Good morning !It is really my honor to have this opportunity for an interview,I hope i can make a good performance today. Im confident that I can su cceed.Now i will introduce myself brieflyI am 26 years old,born in shandong province .I was graduated

17、 from qingdao university. my major is i got my bachelor degree after my graduation in the year of 2003.I spend most of my time on study,i have passed CET4/6 . and i have acq uired basic knowledge of my major during my school time.In July 2003, I began work for a small private company as a technical

18、su pport engineer in QingDao Im capable of more responsibilities, so I deci ded to change my job.And in August 2004,I left QingDao to BeiJing and worked for a foreign e nterprise as a automation software test I want to change my working e nvironment, Id like to find a job which is more challenging.

19、Morover Mot orola is a global company, so I feel I can gain the most from working in this kind of company ennvironment. That is the reason why I come here to compete for this position.I think Im a good team player and Im a person of great honesty to oth ers. Also I am able to work under great pressu

20、re.Thats all. Thank you for giving me the chance.自我介绍(self-introduction) morning. I am glad to be here for this interview. First let me introducemyself. My name is *, 24. I come from *,the capital of *P rovince. I graduated from the * department of *University in July , the past two years I have bee

21、n preparing for the postgraduate exa mination while I have been teaching *in NO.*middle School and I was a head-teacher of a class in junior grade all my hard work has go t a result since I have a chance to be interview by you . I am open-mind ed ,quick in thought and very fond of my spare time,I ha

22、ve broad intere sts like many other like reading books, especially those about *.F requently I exchange with other people by making comments in the foru m on addition ,during my college years,I was once a Net-bar , I have a comparatively good command of network am able to operate the comput er am sk

23、illful in searching for information in am a football fan for tea m is my ,I feel great pity for our countrys team. I always believe that o ne will easily lag behind unless he keeps on learning .Of course, if I am given a chance to study * in this famous University,I will stare no effort to master a

24、good command of advance *.afternoon .I am of great hornor to stand here and introduce myself to y ou .First of all ,my english name is .and my chinese name is .If you are going to have a job interview ,you must say much things which can sho w your willness to this job ,such as ,it is my long cherish

25、ed dream to be.and I am eager to get an opportunity to do.and then give some exa mples which can give evidence to .then you can say something about you r hobbies .and it is best that the hobbies have something to do with the job.What is more important is do not forget to communicate with the intervi

26、 ewee,keeping a smile and keeping your talks interesting and funny can c ontribute to the success.I hope you will give them a wonderful speech .Good luck to you ! morning, my name is jack, it is really a great honor to have this opport unity for a interview, i would like to answer whatever you may r

27、aise, and i hope i can make a good performance today, eventually enroll in this pr estigious university in september. now i will introduce myself briefly,i am 21 years old,born in heilongjiang province ,northeast of china,and i am cu rruently a senior student at beijing XX major is packaging i will

28、receive my bachelor degree after my graduation in the past 4 years,i spend mo st of my time on study,i have passed CET4/6 with an ease. and i have ac quired basic knowledge of packaging and publishing both in theory and in practice. besides, i have attend several packaging exhibition hold in Beiji n

29、g, this is our advantage study here, i have taken a tour to some big fac tory and company. through these i have a deeply understanding of domes tic packaging industry. compared to developed countries such as us, unfor tunately, although we have made extraordinary progress since 1978,our p ackaging i

30、ndustry are still underdeveloped, mess, unstable, the situation of employees in this field are awkard. but i have full confidence in a brigh t future if only our economy can keep the growth pace still. i guess you maybe interested in the reason itch to law, and what is my plan during g raduate study

31、 life, i would like to tell you that pursue law is one of my li felong goal,i like my major packaging and i wont give up,if i can pursue my master degree here i will combine law with my former education. i wi ll work hard in thesefields ,patent ,trademark, copyright, on the base of my years study in

32、 department of p&p, my character? i cannot describe it well, but i know i am optimistic and confident. sometimes i prefer to stay alone, reading, listening to music, but i am not lonely, i like to chat wit h my classmates, almost talk everything ,my favorite pastime is valleyball, playing cards or s

33、urf online. through college life,i learn how to balance b etween study and entertainment. by the way, i was a actor of our amazi ng drama club. i had a few glorious memory on stage. that is my pride.What is your greatest strength?（你最突出的长处是什么？）这是很多面试考官喜欢问的一个问题，这是你展示自己的最佳机缘，不要吹嘘自己或过于 自大，但要让雇主知道你相信自己，你

34、知道自己的长处。如可答：“我以为我最大的长处是 能够执着地尽力把事情办好。当做完一件工作而其功效又正合我的预想时，我会有一种真 正的成绩感。我给自己定了一些高目标。比如说，我要成为超卓的毕业生。虽然在大学一 年级时我启动慢了些，但最终我以优等论文完成了学业。I feel that my strongest asset is my ability to stick to things to get them done. I feel a real sense of accomplishment when I finish a job and it t urns out just as Id pl

35、anned. Ive set some high goals for myself. For exa mple, I want to graduate with highest distinction. And even though I had a slow start in my freshman year, I made up for it by doing an honors thesis.What is your greatest weakness?（你最大的弱点是什么？）你不该该说你没有任何弱点，以此来回避这个问题。每一个人都有弱点，最佳策略是承认 你的弱点，但同时表明你在予以改良

36、，并有克服弱点的计划。可能的话，你可说出一项可 能会给公司带来益处的弱点，如可说：“我是一个完美主义者。工作做得不漂亮，我是不会 撒手的。Im such a perfectionist that I will not stop until a job is well done. 英语面试实战指南I： Interviewer（面试者）A： Applicant（求职者）介绍教育背景：简明扼要，实话实说虽然你在简历中对自己的教育背景作了介绍，但在面试时，面试官还有可能就此方面提问。 仍是事前做点准备吧。11 I what is your major?A My major is Business Ad

37、ministration. I am especially interested in Ma rketing .（不仅回答了问题，还顺便一句介绍了自己较为感兴趣的方面，简明扼要。）I Which university are you attending？A I am attendingx x xUniversity.I Have you received any degrees？A Yes. First I received my Bachelor degree in English Literature and th en an MBA degree.I What course did yo

38、u like best？A Project Management. I was very interested in this course when I was a student. And I think its very useful for my present work.I Do you feel that you have received a good general training？A Yes I have studied in an English train-ing program and a computer tr aining program since I grad

39、uated from university. I am currently studyingFinance at a training school.介绍工作经验：显露实力，避免炫耀I Have you ever been employed？I Your resume says you have had one-year experience working in a fo reign representative office in Shanghai may I ask why you left？A I worked in a foreign for one I left there two

40、 years ago because th e work they gave me was rather found another job that is more interest ing.I Have you done any work in this field？I What qualifications do you have that make you feel you will be succ essful in your field？I What have you learned from the jobs you have had？A I have learned a lot

41、 about business know how and basic office skills. In addition I learned at my previous job show to cooperate with my coll eagues.I Whats you major weak point?A I havent been involved in international business so I dont have any experience but I have studied this course in the International Business

42、T raining Center of thexx xCompany.I What are your greatest strengths?（实话实说好了，没必要客气，但应注意语 气和表情，不要给人炫耀之感。）I Please tell me about your working experience.I Does your present employer know you are looking for another job？A No I havent discussed my career plans with my present employer b ut I am sure he

43、 will understand.性格爱好：表现踊跃、合作的一面I How do you spend your spare time？I Are you interested in sports？I Do you think you are introverted or extroverted？I What kind of personality do you think you have？A I always approach things very enthusiastically. When I beg in somethi ng I dont like to leave it half

44、done. I cant concentrate on something ne w until the first thing is finished.I What is the most important thing for you to be happy？A Different people have different ideas. I think the most important thing for me is having a good relationship with my family members and my fri ends. My family has alw

45、ays been very closeknit and my friend sand I sp end a lot of time together. Without that I would be much less happy tha n I am.I What makes you angry？A Dishonesty. Its unacceptable.I What are your personal weaknesses?A Im afraid Im a poor talker. Im not comfortable talking with the peo ple whom I ha

46、ve just met for the first time. That is not very good for bu siness so I have been studying public speaking.I Are you more of a leader or a follower?A I dont try to lead people. Id rather cooperate with everybody and g et the job done by working together.工作要求：我能胜任I Do you think you can make yourself

47、 easily understood in English?A Yes in most circumstances.I Are you available for travel？A Yes I like traveling. I am young and unmarried. Its no problem for me to travel frequently.I How about overtime work？A Overtime work is very common in companies. I can work overtime if i ts necessary but I don

48、t think we will work overtime everyday.I How long do you think we can depend on your working here？I Do you like regular work？A No I dont like regular work. I am interested in different projects wit h new opport unities and new challenge but I can do regular work if th e company needs me to do so.I W

49、hat salary do you expect？A Shall we discuss my responsibilities with your company first？ I think s alary is closely related to the responsibilities of the job.I Do you work well under pressure？A Working under pressure is exciting and challenging. I dont mind work ing under pressure. I work well unde

50、r the secircum stances. People can I Can.I Do you have any particular conditions that you would like the compa ny to take into consideration?A No nothing in particular.I How soon can you begin working for us?A I need about two to three weeks for necessary formalities. I will quit then transfer to yo

51、ur company.面试结束：礼貌道别I Any questions?A When will I know your decision?I How can we get in touch with you?I We will notify you of our decision by mail is this convenient for yo u?I Thank you for your interest in our company.A Thank you . Goodbye. Thank you for your time.I You will be hearing from us very soon. Please send the next applica ntin on your way out.A you very much.另外，面试官还可能问及你的家庭情况，如家人对你的影响等，也应事前有所准备。资料：英语自我介绍常常利用十句话I have been for over five years in teh employ of an exporting compan y.本人曾经前后五年被受雇于出口贸易公司。I have been in the b