蓝牙及其射频技术.doc

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讯技术标准，具有广泛的应用前景，正受到全球各界的广泛关注。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交换及文件同步，使移动电话、便携式计算机以及各种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讯与链接，且能在移动中进行无线连接和通讯；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，就可以实现有线局域网的无线数据连接；支持电路交换与分组交换，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，具有极其广泛的应用前景。
2 蓝牙技术概况
        2.1 蓝牙的起源
        蓝牙的名字来源于10世纪丹麦国王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1.0B版。发展至今，加盟的公司已超过2000多家。一项公开的全球统一的技术规范能得到工业界如此广泛的关注和支持是前所未有的。当然，这主要得益于蓝牙技术本身所具有的广阔应用前景和诱人的商机。
        2.2 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，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网络，使得近距离内各种信息设备能够实现无缝资源共享。
        2.2 蓝牙系统的参数指标及组成
        2.2.1 蓝牙系统结构基本系统参数及指标
        工作频段：ISM频段2.402GHz—2.480GHz
        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723.2kbit/s  57.6kbit/s
        对称连接：433.9kbit/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
        信道数：79
        发射功率及覆盖：0dBm(1mW)，1—10m覆盖，20dBm(100mW)，扩展至100m覆盖
        跳频频点数：79个频点/MHz(2402+k)MHz，（k=0，1，2……78)；
        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)、无连接业务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)，CRC—16，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。
        2.3 蓝牙系统的组成
        蓝牙系统由无线单元、链路控制单元、链路管理和软件结构和协议体系组成。
        2.3.1 无线单元 蓝牙天线属于微带天线，空中接口是建立在天线电平为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。
        2.3.2 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理规范。
        2.3.3 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。
        2.3.4 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，扩大了使用的带宽。蓝牙使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更加可靠。
3．1蓝牙的频带和信道分配
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。信道分配为厂一(2 402+k)MHz，其中k一0，⋯ ，78，共79个信道，79个跳频频点最大的跳频速率为1 660跳／秒。信道间隔为1 MHz。共享一个公共信道的所有蓝牙单元形成一个微网，每个微网最多可以有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保持同步。
3．2蓝牙射频收发技术特性
蓝牙采用时分双工传输方案，使用一个天线利用不同的时间间隔发送和接收信号，且在发送和接收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1，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1 mw，无线通信距离为10 m，数据传输速率达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100 m，数据传输速率也达到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。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还是减少。如果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，蓝牙标准还对收发过程的寄生辐射、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
蓝牙无线技术使用串行通信，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 蓝牙模块的构成

就蓝牙射频模块来说，为了在提高收发性能的同时减小器件的体积和成本，各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。但就其基本原理来说，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。各部分的主要功能如下：
(1)接收模块 当射频模块在接收模式下时，信号由天线接收，经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(这样可以得到较高的共模抑制比)；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。
(2)发送模块 当射频模块在发送模式下，数据由基带模块输入，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。
(3)合成器 合成器是收发模块中最关键的部分。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保持。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。他将信号反馈至解调电路，最终发送至基带处理芯片，以便根据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(将基带蓝牙处理器、链路管理及微控制器集为一身，有的还集成Flash存储器)。这类模块技术成熟，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射频收发器构成；
爱立信蓝牙模块ROK101007由射频模块PBA313系列和基带控制器组成；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理电路、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。这类模块起步较晚，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电子公司也声称推出迄今为止最小的蓝牙模块。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”便于使用，并且还有利于减小体积、功耗和成本，有利于蓝牙集成在其他设备如手机、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器件和基带部分相分离，就可以使各公司发挥其所长。通过标准接口，用户可以根据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，应该根据自己系统的实际要求选择单芯片结构还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、蓝牙技术和其他短距离无线技术相比(如：IEEE 802．1lb，HomeRF，IrDA)的优势还存在很大的争议。但是，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，就一直被人们寄予了极高的期望。相信随着科技的进一步发展，蓝牙技术必将获得更加广泛的应用。
参考文献
[1] 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
[2] 金纯，许光辰，孙睿．蓝牙技术[M]．北京：电子工业出版社，2001
[3] 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：
通信工程
班级学号：
4070709
姓 名：
曾庆东
指导教师：
高军
时 间：
2010/6/16~2010/6/23

Good morning !
It is really my honor to have this opportunity for an interview,
I hope i can make a good performance today. I'm confident that I can succeed.
Now i will introduce myself briefly
I am 26 years old,born in shandong province .
I was graduated from qingdao university. my major is electronic.and 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 acquired basic knowledge of my major during my school time.
In July 2003, I began work for a small private company as a technical support engineer in QingDao city.Because I'm capable of more responsibilities, so I decided to change my job.
And in August 2004,I left QingDao to BeiJing and worked for a foreign enterprise as a automation software test engineer.Because I want to change my working environment, I'd like to find a job which is more challenging. Morover Motorola 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 I'm a good team player and I'm a person of great honesty to others. Also I am able to work under great pressure.
That’s all. Thank you for giving me the chance.

自我介绍(self-introduction)
1.Good morning. I am glad to be here for this interview. First let me introduce myself. My name is ***, 24. I come from ******,the capital of *******Province. I graduated from the ******* department of *****University in July ,2001.In the past two years I have been preparing for the postgraduate examination while I have been teaching *****in NO.****middle School and I was a head-teacher of a class in junior grade two.Now all my hard work has got a result since I have a chance to be interview by you . I am open-minded ,quick in thought and very fond of history.In my spare time,I have broad interests like many other youngsters.I like reading books, especially those about *******.Frequently I exchange with other people by making comments in the forum on line.In addition ,during my college years,I was once a Net-bar technician.So, I have a comparatively good command of network application.I am able to operate the computer well.I am skillful in searching for information in Internet.I am a football fan for years.Italian team is my favorite.Anyway,I feel great pity for our country’s team. I always believe that one 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 good command of advance ******.

2.Good afternoon .I am of great hornor to stand here and introduce myself to you .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 show your willness to this job ,such as ,it is my long cherished dream to be ...and I am eager to get an opportunity to do...and then give some examples which can give evidence to .then you can say something about your 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 interviewee,keeping a smile and keeping your talks interesting and funny can contribute to the success.
I hope you will give them a wonderful speech .Good luck to you !
3.good morning, my name is jack, it is really a great honor to have this opportunity for a interview, i would like to answer whatever you may raise, and i hope i can make a good performance today, eventually enroll in this prestigious university in september. now i will introduce myself briefly,i am 21 years old,born in heilongjiang province ,northeast of china,and i am curruently a senior student at beijing XX uni.my major is packaging engineering.and i will receive my bachelor degree after my graduation in june.in the past 4 years,i spend most of my time on study,i have passed CET4/6 with an ease. and i have acquired basic knowledge of packaging and publishing both in theory and in practice. besides, i have attend several packaging exhibition hold in Beijing, this is our advantage study here, i have taken a tour to some big factory and company. through these i have a deeply understanding of domestic packaging industry. compared to developed countries such as us, unfortunately, although we have made extraordinary progress since 1978,our packaging industry are still underdeveloped, mess, unstable, the situation of employees in this field are awkard. but i have full confidence in a bright 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 graduate study life, i would like to tell you that pursue law is one of my lifelong goal,i like my major packaging and i won't give up,if i can pursue my master degree here i will combine law with my former education. i will work hard in thesefields ,patent ,trademark, copyright, on the base of my years study in 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 with my classmates, almost talk everything ,my favorite pastime is valleyball,playing cards or surf online. through college life,i learn how to balance between study and entertainment. by the way, i was a actor of our amazing drama club. i had a few glorious memory on stage. that is my pride.

3. What is your greatest strength?（你最突出的优点是什么？）
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会，不要吹嘘自己或过于自负，但要让雇主知道你相信自己，你知道自己的优点。如可答：“我认为我最大的优点是能够执着地尽力把事情办好。当做完一件工作而其成果又正合我的预想时，我会有一种真正的成就感。我给自己定了一些高目标。比如说，我要成为出色的毕业生。尽管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 turns out just as I’d planned. I’ve set some high goals for myself. For example, 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 honor’s thesis.
4. What is your greatest weakness?（你最大的弱点是什么？）
你不应该说你没有任何弱点，以此来回避这个问题。每个人都有弱点，最佳策略是承认你的弱点，但同时表明你在予以改进，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好处的弱点，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。”
I'm 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

尽管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。还是事先做点准备吧。

①Iwhat is your major？

AMy major is Business Administration. I am especially interested in〃Marketing〃.

(不仅回答了问题，还顺带一句介绍了自己较为感兴趣的方面，简明扼要。)

②IWhich university are you attending？

AI am attending×××University.

③IHave you received any degrees？

AYes. FirstI received my Bachelor degree in English Literatureand then an MBA degree.

④IWhat course did you like best？

AProject Management. I was very interested in this course when I was a student. And I think it’s very useful for my present work.

⑤IDo you feel that you have received a good general training？

AYesI have studied in an English training program and a computer training program since I graduated from university. I am currently studying Finance at a training school. 介绍工作经验：显露实力，避免炫耀

①IHave you ever been employed？

②IYour resume says you have had one-year experience working in a foreign representative office in Shanghaimay I ask why you left？

AI worked in a foreign rep.office for one year.HoweverI left there two years ago because the work they gave me was rather dull.I found another job that is more interesting.

③IHave you done any work in this field？

④IWhat qualifications do you have that make you feel you will be successful in your field？

⑤IWhat have you learned from the jobs you have had？

AI have learned a lot about business know how and basic office skills. In additionI learned at my previous job show to cooperate with my colleagues.

⑥IWhat’s you major weak point？

AI haven’t been involved in international businessso I don’t have any experiencebut I have studied this course in the International Business Training Center of the×××Company.

⑦IWhat are your greatest strengths？(实话实说好了，不必客气，但应注意语气和表情，不要给人炫耀之感。)

⑧IPlease tell me about your working experience.

⑨IDoes your present employer know you are looking for another job？

ANoI haven’t discussed my career plans with my present employerbut I am sure he will understand. 性格爱好：表现积极、合作的一面

①IHow do you spend your spare time？

②IAre you interested in sports？

③IDo you think you are introverted or extroverted？

④IWhat kind of personality do you think you have？

AI always approach things very enthusiastically. When I beg in somethingI don’t like to leave it halfdone. I can’t concentrate on something new until the first thing is finished.

⑤I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 friends. My family has always been very closeknitand my friend sand I spend a lot of time together. Without that I would be much less happy than I am.

⑥IWhat makes you angry？

ADishonesty. It’s unacceptable.

⑦IWhat are your personal weaknesses？

AI’m afraid I’m a poor talker. I’m not comfortable talking with the people whom I have just met for the first time. That is not very good for businessso I have been studying public speaking.

⑧IAre you more of a leader or a follower？

AI don’t try to lead people. I’d rather cooperate with everybodyand get the job done by working together. 工作要求：我能胜任

①IDo you think you can make yourself easily understood in English？

AYesin most circumstance