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specific absorption rate是什么意思
中文翻译吸收速率比值:&&&&adj. 1.特殊的；特有的；特定的，专门的。 2.明确 ...:&&&&n. 1.吸收，合并。 2.专心，一心不乱，热中 (in ...:&&&&vt.,vi. 〔方言〕＝ret.
例句与用法1.The exposure standard for mobile phones employs a unit of measurement known as the specific absorption rate , or sar流动电话的暴露标准运用了一组名为特定吸收率的测量数据,即sar 。 2.Finally , the concrete electromagnetic environment was discussed , and the result of specific absorption rate was given in this paper最后根据具体的电磁环境进行了讨论，并计算了比吸收率。 3.Basic standard for the measurement of specific absorption rate related to human exposure to electromagnetic fields from mobile phones 300 mhz - 3 ghz通话人暴露于电磁场的移动电话特殊吸收测量基本标准4.Sar : practice for determining the peak spatial - average specific absorption rate in the human head from wireless communications devices : measurement techniques测定人体头部中来自无线通信装置的峰值空间平均比吸附率5.Sar : recommended practice for determining the peak spatial - average specific absorption rate in the human head from wireless communications devices : measurement techniques人脑对无线通信设备的峰值空间-平均绝对吸收率6.Sar safety levels with respect to human exposure to radio frequency electromagnetic fields , 3 khz to 300 amendment 2 : specific absorption rate limits for the pinna处于射频电磁场3khz至300ghz的人体的安全等级.修改件2 : pinna的特定吸收率7.Comparing to traditional external antennas , internal antennas offer several advantages , such as less broken off , low specific absorption rates ( sar ) , easy mass production与传统外置天线相比,内置天线有着非常诱人的好处,如不易跌破,低特定吸收率( sar ) ,易实现大规模批量生产。 8.300 mhz 3 ghz human exposure to radio frequency fields from hand - held and body - mounted wireless communication devices - human models , instrumentation , and procedures - part 1 : procedure to determine the specific absorption rate for hand - held devices used in close proximity to the ear frequency range of 300 mhz to 3 ghz人暴露于手持和车载无线通信设备产生的射频场.人体模型仪器和规程.第1部分:紧贴耳朵使用的手持设备9.In this paper , the calculation is made of the electric stress distribution and specific absorption rate ( sar ) distribution in the human body exposed to the stable plane wave and nuclear explosion electromagnetic pulse and microwave weapon electromagnetic pulse本文主要讨论了振幅为100 、随正弦规律变化的稳态平面波、核爆炸脉冲波和微波武器脉冲波作用下人体内的电场应力的分布，同时也给出了在上述电磁波的作用下sar (比吸收率)的分布。
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合作伙伴：&&n. Intel 所采用的一种节省澳电的技术.在 600MHz 以上的 Mobile Pentium III 处理器, 设计了两组 PLL 时脉输入线路, 可以支持两种不同核心电压/时脉的组合配对.一种是6V 核心电压,最大效能 (Maximum Performance) 模式 (100%); 另一种是电池最佳化 (Battery Optimized) 模式, 这时候 CPU 的时脉通常只有 80% 左右, 其中核心电压可降到35V.而且两种操作模式的切换时间只需两千分之一秒的时间.以 Intel 的资料表示: 操作频率降低 20%, 再配合核心电压的降低, 理论上耗电量可以降低到原先操作模式的五到六成之间.以 600MHz 的笔记型 Pentium III 为例, 在我们外出携带笔记型计算机时, 通常不会去接 AC Power 交流电电源, 此时笔记型计算
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step time是什么意思
中文翻译分步时间，把固定的一段时间长短平分为数段，通常在鼓机上，需要这种功能来一步步设置:&&&&vi. (-pp-) 1.走；跨步。 2.踩，踏上 (o ...:&&&&n. 1.时，时间，时日，岁月。 2.时候，时刻；期间； ...
例句与用法1.The design on a kind auto - weight and packing machine by three - step timing一种三级控制自动定量包装机的设计2.Step time changes are the first and most common method of simulated moving bed tuning改变步进时间，是最首要最常用的调整模拟移动床的方法。 3.Habit is habit , and not to be flung out of the window by any man , but coaxed downstairs a step time习惯就习惯，谁也不能将其扔出窗外，只能一步一步地引它下楼。 4.In this paper we adopt this new chain to construct chained dls - icbp network and greatly boost the performance of multi - steps time series prediction实验证实基于dls的新型链结构网络较传统的dls - icbp和icbp链结构网络的多步预测性能有较大提高。 5.In this article , we applied our improved circular back - propagation ( icbp ) network to single step and multi - steps time series prediction respectively在本文中将我们改进的圆形反向传播网络模型( improvedcircularbackpropagation - - icbp )应用于时间序列预测，进行了单步和多步时间序列预测研究。 6.An incrementally - iterative algorithm with constant stiffness , which combines step - by - step time integration scheme with unbalanced load transfer method , is employed in numerically implementing of the proposed constitutive model在模型本构关系的数值实施中，采用将时域逐步积分格式与不平衡荷载转移法相结合的增量?常刚度迭代算法。 7.And the waveform of the transmitted signals was designed based on the target distance ( 5 ~ 50m ) . the waveform is triangular fmcw with central frequency at 6ghz , modulation bandwidth 100mhz , modulation period 10 s , step frequency 0 . 2mhz , and step time 10ns在此基础上,设计发射信号波形参数为三角形调频连续波,中心频率6ghz ,调制带宽100mhz ,调制周期10 s ,步进频率0 . 2mhz ,步进时间10ns 。 8.On the other hand , in winter , it should be taken the adequate change in production techniques such as the increase of pit entry temperature in the first steamer , the decrease of pit stepping times , the addition of saccharifying enzyme and dry yeast , and the increase of starch content etc . to ensure good fermentation of fermented grains and further to stablize and improve product quality同时，在冬季生产中，要采取适当提高第一甑大（米查）的入池温度、减少殊窖、添加糖化酶和干酵母、提高淀粉浓度等工艺措施，保证粮醅的良好发酵，稳定和提高产品质量。 9.( 2 ) it explains the basic concept of time series , some kinds of the common time series models and the development characteristics of time series in detail . it analyses how to judge the model from the self - related function and the deviation related function . determining a better standard to set up models from the comparison of some kinds of fixed step time series standards , then predicts utilizing the counter function( 2 )详细阐明了时间序列的基本思想、几种常见的时间序列模型以及时间序列的动态特征，分析了如何利用自相关函数和偏相关函数来对模型进行判定，通过对时间序列的几种定阶准则的比较，确定一种好的定阶准则来建立模型，从而可以利用逆函数法进行预报。
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淘豆网网友近日为您收集整理了关于蓝牙设备怎样工作——通信类外文文献翻译、中英文翻译的文档，希望对您的工作和学习有所帮助。以下是文档介绍：蓝牙设备怎样工作——通信类外文文献翻译、中英文翻译 中北大学 2006 届本科毕业设计说明书第 1 页共 14 页How Bluetooth WorksChatschik BisdikianThere are lots of different ways that electronic devices can connect to one another.For example:Many puter systems have a CPU unit connected to a mouse, akeyboard, a printer and so on.. A personal digital assistant (PDA) will normallyconnect to puter with a cable and a docking cradle. A TV will normallyconnect to a VCR and a cable box, with a remote control for all ponents. Acordless phone connects to its base unit radio waves and it may have a headset thatconnects to the phone with a wire. In a stereo system, a CD player and other audiodevices connect to the receiver, which connects to the speakers. When you puters, entertainment systems or telephones, the various pieces and parts of thesystems make up munity of electronic devices. These municatewith each other using a variety of wires, cables, radio signals and infrared light beams,and an even greater variety of connectors, plugs and protocols.The art of connecting things is ing more and plex every day. Wesometimes feel as if we need a Ph.D. in electrical engineering just to set up theelectronics in our homes! In this article, we will look at pletely different way toform the connections, called Bluetooth. Bluetooth is wireless and automatic, and has anumber of interesting features that can simplify our daily lives.The ProblemsWhen any two devices need to talk to each other, they have to agree on a numberof points before the conversation can begin. The first point of agreement is physical:Will they talk over wires, or through some form of wireless signals? If they use wires,how many are required – one, two, eight, 25? Once the physical attributes are decided,several more questions arise:Information can be sent 1 bit at a time in a scheme called munications, or in groups of bits (usually 8 or 16 at a time) in a scheme munications. . A puter uses both serial and munications to talk to different devices: Modems, mice and keyboards tend totalk through serial links, while printers tend to use parallel links.All of the parties in an electronic discussion need to know what the bits mean andwhether the message they receive is the same message that was sent. In most cases,this means developing a language mands and responses know as a protocol.Some types of products have a standard protocol used by virtually panies sothat mands for one product will tend to have the same effect on another.Modems fall into this category. Other product types each speak their own language,which means mands intended for one specific product will seem gibberish ifreceived by another. Printers are like this, with multiple standards like PCL panies that puters, entertainment systems and otherelectronic devices have realized that the incredible array of cables and connectorsinvolved in their products makes it difficult for even expert technicians to correctlyset up plete system on the first try. Setting puter and home entertainment中北大学 2006 届本科毕业设计说明书第 2 页共 14 页system es plicated when the person buying the equipment has tolearn and remember all the details to connect all the parts. In order to make homeelectronic more user friendly, we need a better way for all the electronic part of ourmodern life to talk to each other. That’s where es in.Bluetooth BasicsBluetooth is a standard developed by a group of electronics manufacturers thatallows any sort of electronic equipment –puter and cell phones to keyboardsand headphones –to make its own connections, without wires, cables or any directaction from a user. Bluetooth is intended to be a standard that works at two levels: Itprovides agreement at the physical level –Bluetooth is a radio-frequency standard . Italso provides agreement at the next level up , where products have to agree on whenbits are sent, how many will be sent at a time and how the parties in conversation canbe sure that the message received is same as the message sent.panies belonging to the Bluetooth Special Interest Group, and there aremore than 1,000 of them, want to let Bluetooth’s munications take the placeof wires for connecting peripherals, telephones puters.Other Wireless ConnectionsThere are already a couple of ways to get around using wires. One is to carryinformation puters via beams of light in the infrared spectrum. Infraredrefers to light waves of a lower frequency than human eyes can receive and interpret..Infrared is used in most television remote control systems, and with a standard calledIrDA (Infrared Data Association) it`s used to connect puters with peripheraldevices. For most of puter and entertainment purposes, infrared is used in adigital mode – the signal is pulsed on and off very quickly to send data from one pointto another.munications are fairly reliable and don`t cost very much to buildinto a device, but there are a couple of drawbacks. First, infrared is a ―line of sight‖technology. For example, you have to point the remote control at the television orDVD player to make things happen. The second drawback is that infrared is almostalways a ―one to one‖ technology. You can send data between your puterand your puter, but not your puter and your PDA at the time.These two qualities of infrared are actually advantageous in some regards.Because infrared transmitters and receivers have to be lined up with each other,interference between devices is mon. The one-to-one nature of munications is useful in that you can make sure a message goes only to theintended recipient, even in a room full infrared receivers.The Bluetooth SolutionBluetooth is intended to get around the problems e with both infraredand cable synchronizing systems. The hardware vendors, which include Siemens,Intel, Toshiba, Motorola and Ericsson, have developed a specification for a very smallradio module to be built puter, telephone and entertainment equipment. Fromthe user`s point of view, there are three important features to Bluetooth:It`s wireless. When you travel, you don`t have to worry about keeping track of abriefcase full of cables to attach all of ponents, and you can design your中北大学 2006 届本科毕业设计说明书第 3 页共 14 页office without wondering where all the wires will go.It`s inexpensive.You don`t have to think about it. Bluetooth doesm`t require you to do anythingspecial to make it work. The devices find one another and strike up a conversationwithout any user input at all.Bluetooth municates on a frequency of 2.45 gigahertz, which has been setaside by international agreement for the use of industrial, scientific and medicaldevices (ISM).A number of devices that you may already use take advantage of this sameradio-frequency band. Baby monitors, garage-door openers and the newest generationof cordless phones all make use of frequencies in the ISM band. Making sure thatBluetooth and these other devices don`t interfere with one another has been a crucialpart of the design process.Avoiding Interference: Low PowerOne of the ways Bluetooth devices avoid interfering with other system is bysending out very weak signals of 1 milliwatt. puter, the most powerful cellphones can transmit a signal of 3 watts. The low power limits the range of a Bluetoothdevice to about 10 meters, cutting the chances of interference between putersystem and your portable telephone or television. Even with the low power, the wallsin your house won`t stop a Bluetooth signal, making the standard useful forcontrolling several devices in different rooms.With many different Bluetooth devices in a room, you might think they`d interferewith one another, but it`s unlikely. On the next page, we`ll see why.Avoiding Interference: HoppingIt is unlikely that several devices will be on the same frequency at the sametime, because Bluetooth uses a technique called spread-spectrum frequency hopping.In this technique, a device will use 79 individual, randomly chosen frequencies withina designated range, changing from one to another on a regular basis. In the casa ofBluetooth, the transmitters change frequencies 1,600 times every second, meaningthat more devices can make full use of a limited slice of radio spectrum. Since everyBluetooth transmitter uses spread-spectrum transmitting automatically, it unlikely thattwo transmitters will be on the same frequency at the same time. This same techniqueminimizes the risk that portable phones or baby monitors will disrupt Bluetoothdevices, since any interference on a particular frequency will last only a tiny fractionof a second.When Bluetooth-capable e within range of one another, anelectronic conversation takes place to determine whether they have data to share orwhether one needs to control the other. The user doesn`t have to press a button or mand – the electronic conversation happens automatically. Once theconversation has occurred, the devices – whether they`re part of puter system ora stereo – form work. Bluetooth systems create a personal-work (PAN),or , that may fill a room or may pass no more distance than that betweenthe cell phone on a belt-clip and the headset on your head. Once a
is中北大学 2006 届本科毕业设计说明书第 4 页共 14 页established, the members randomly hop frequencies in unison so they stay in touchwith one another and avoid other s that mat be operating in the same room.Example: NetworksLet`s take a look at how the Bluetooth frequency hopping and personal-work keep system from ing confused. Let`s say you`re got a typical modernliving room with the typical modern stuff inside. There`s an entertainment systemwith a stereo, a DVD player, a satellite TV recei there`s cordlesstelephone and a puter. Each of these systems uses Bluetooth, and eachforms its own
to talk between main unit and peripheral.The cordless telephone has one Bluetooth transmitter in the base and another inthe handset. The manufacturer has programmed each unit with an address that fallsinto a range of addresses it has established for a particular type of device. When thebase is first turned on, it sends radio signals asking for a response from any units withan address in a particular range. Since the handset has an address in the range, itresponds, and a work is formed. Now, even if one of these devices shouldreceive a signal from another system, it will ignore it since it`s not from within work. puter and entertainment system go through similar routines,works among address in ranges established by manufacturers. works are established, the systems begin talking among themselves.
hops randomly through the available frequencies, so all of the s pletely separated from one another.Now the living room has three work established , each one made up ofdevices that know the address of transmitters it should listen to and the address ofreceivers it should talk to.Since work is changing the frequency of itsoperation thousand of times a second, it’s unlikely that any work will be on thesame frequency at the same time. If it turns out that they are, then the resultingconfusion will only cover a tiny fraction of a second, and software designed to correctfor such errors weeds out the confusing information and gets on work’sbusinessExample:Half/Full DuplexMost of the time,work munications method either works in onedirection at a time, called half-munication, or in both directionsimultaneously, called full-munication. A speakerphone that lets you eitherlisten or talk, but not both ,is an example of half-munication, while aregular telephone handset is a full-duplex device.Beacause Bluetooth is designed towork in a number of different circumstances, it can be either half-duplex orfull-duplex.The cordless telephone is an example of a use that will call for a full-duplex(two-way) link, and Buletooth can send data at more than 64,000 bits per second in afull-duplex link—a rate high enough to support several human voice conversation.If a particular use calls for a half-duplex link—connecting to puter printer, forexample—Bluetooth can transmit up to 721 kilobits per second(Kbps) in onedirection,with 57.6 Kps in the other. If the use calls for the same speed in bothdirections, a link with 432.6-Kbps capacity in each direction can be made.中北大学 2006 届本科毕业设计说明书第 5 页共 14 页Bluetooth SpaceHere are some specification details from the Bluetooth Web siteThe devices in a
share munication data channel. The channelhas a total capacity of 1 megabit per second (Mbps). Headers and handshakinginformation consume about 20 percent of this capacity.In the United States and Europe, the frequency range is 2,400 to 2,483.5 MHz, with79 1-MHz radio frequency (RF) channels. In practice, the range is 2,402 MHz to2,480 MHz. In Japan, the frequency range is 2,497 MHz with 23 1-MHz rf channels.A data channel hops randomly 1,600 times per second between the 79 (or 23) RFchannels.Each channel is divided into time slots 625 microseconds long.A
has a master and up to seven slzves.Packets can be up to five time slots wide.Data in a packet can be up to 2,745 bits in length.There are currently two types of data transfer between devices: SCO ( synchronousconnection oriented) and ACL (asynchronous connectionless).In a , there can be up to three SCO links of 64,000 bits per second each. Toavoid timing and collision problems, the SCO links use reserved slots set up by themaster.Masters can support up to three SCO links with one, two or three slaves.One master and slave can have a single ACL link.ACL is either point-to-point (master to one slave) or broadcast to all the slaves.ACL slaves can only transmit when requested by the master.The heart of the Bluetooth specification is the Bluetooth protocol stack. Byproviding well-defined layers of functionality, the Bluetooth specification ensuresinteroperability of Bluetooth devices and encourages adoption of Bluetoothtechnology.As you can see in figure 1-1, these layers range from the low-level radio link to theprofiles.Figure 1-1:The Bluetooth protocol stackLower Layers中北大学 2006 届本科毕业设计说明书第 6 页共 14 页At the base of the Bluetooth protocol stack is the radio layer. The radio modulein a Bluetooth device is responsible for the modulation and demodulation of data intoRF signals for transmission in the air. The radio layer describes the physicalcharacteristics a Bluetooth device`s receiver-ponent must have. Theseinclude modulation characteristics, radio frequency tolerance, and sensitivity level.Above the radio layer is the baseband and link controller layer. The Bluetoothspecification doesn`t establish a clear distinction between the responsibilities of thebaseband and those of the link controller. The best way to think about it is that thebaseband portion of the layer is responsible for properly formatting data fortransmission to and from the radio layer. In addition, it handles the synchronization oflinks. The link controller portion of this layer is responsible for carrying out the linkmanager`mands and establishing and maintaining the link stipulated by linkmanager.The link manager itself translates the host controller interface (HCI) commandsit receives into baseband-level operations. It is responsible for establishing andconfiguring links and managing power-change requests, among other tasks.You`ve noticed links mentioned numerous time in the preceding paragraphs. TheBluetooth specification defines two types of links between Bluetooth devices:Synchronous, Connection-Oriented (SCO), for isochronous and munication using, for example, headsetsAsynchronous, Connectionless (ACL), for munication, such as theexchange of vCards.Each link type is associated with a specific packet. A SCO link provides reservedchannel bandwidth munication between a master and a slave, and supportsregular, periodic exchange of data with no retransmission of SCO packets.An ACL link exists between a master and a slave the moment a connection isestablished. The data packets Bluetooth uses for ACL links all have 142 bits ofencoding information in addition to a payload that can be as large as 2712 bits. Theextra amount of data encoding heightens transmission security. It also helps tomaintain a munication link in an environment fill with other devices mon noise.The HCI (host controller interface) layer acts as a boundary between the lowerlayers of the Bluetooth protocol stack and upper layers The Bluetooth specificationdefines a standard HCI to support Bluetooth systems that are implemented across twoseparate processors, For example, a Bluetooth system puter might use aBluetooth module`s processor to implement the lower layers of the stack (radio,baseband, link controller, and link manager). It might then use its own processor toimplement the upper layers (L2CAP, M, OBEX, and selected profiles). Inthis scheme, the lower portion is known as the Bluetooth module and the upperportion as the Bluetooth host.Of course, it`s not required to partition the Bluetooth stack in this way. Bluetoothheadsets, for example, combine the module and the host portions of stack on oneprocessor because they need to be small and self-contained. In such devices, the HCImay not be implemented at all unless at all unless device testing is required.中北大学 2006 届本科毕业设计说明书第 7 页共 14 页Because the Bluetooth HCI is well defined, you can write drivers that handledifferent Bluetooth modules from different manufacturers. Apple provides an HCIcontroller object that supports a USB implementation of the HCI layer. .ReferencesBN. Sklavos et al., &Random Number Generator Architecture and VLSIImplementation,&Proc. IEEE Int'1 Symp. Circuits &Systems (ISCAS 02), IEEE Circuits andSystems So Bluetooth Bluetooth SIG security expert group.c. Press, Piscataway, N.J., 2002, pp.854-857.M. Abramovici, M.A. Breuer, and A.D. Friedman, Digital Systems Testing and Testable Design,IEEE Press, Piscataway, N.J., 1990.P. Chandrakasan, S. Sheng, and R. W.Brodersen, &Low Power CMOS Digital Design,& IEEE J.Solid-State Circuits, vo1.27, no. 4, Apr. 1992, pp. 473-X84.J.L. Massey, G.H. Khachatrian, and M.K.Kuregian, &Nomination of SAFER+ as CandidateAlgorithm for the Advance Encryption Standard,& Proc. 1 st AdvancedEncryption Standard Candidate Conf., 1998;on.edu/}rblee/safer+.Bluetooth SIG, Specification of the Bluetooth system, Core, Part B;'Baseband specification';Version 1 .1, 22 February 2001, at 血S.Sengodan,T.Luo,R.Bansal,H.H &End-to-end Security Issues Wireless-works,‖IASTED Applied Informatics,Austria,February in 15-17,2000M.Bellare,R.ti,H.Krawczykz, &Keying Hash Functions for MessageAuthentication,&Advances in Crypto 96 Proceedings ,Lecture Notes puter SciencesVo1.1109,N.Koblitz ed.,Springer-Verlag,1996中北大学 2006 届本科毕业设计说明书第 8 页共 14 页蓝牙设备怎样工作在电气设备中存在很多种连接方式。例如:许多台式计算机系统有一个 CPU单位连接到鼠标、键盘、打印机等等。个人数字助理(PDA)通常将一根电缆和一个连接设备接在计算机上。电视通常连接着录像机和一个线盒, 对三种成分实现细微的控制。无绳电话利用无线电波和其基座单元连接在一起,它有一个头戴式耳机用一根导线连接到电话上。在立体声系统中,CD 唱机和其他的声音设备连接到接收器上,接收器连接到扬声器。当使用电脑、娱乐设备或者电话的时候,各种小的系统组成了整个电子器件。这些装置通过金属丝、电缆、无线电信号和红外线以及多种连接器、插头和协议相互通信。设备之间的连接现在正变得越来越复杂。有时候我们感觉为了在家里建立电气化我们似乎需要一个电机工程中的PhD.。在这篇文章中,我们将看到一种完全不同的连接方式——蓝牙。蓝牙是一种无线的自动化装置,它有很多能使我们日常生活简化的有趣的特点。问题在于当两个设备之间要进行通信的时候,在通信开始之前,它们不得不相互统一很多的因素。第一点是物理的协议:它们是用线缆还是无线信号?如果他们用电缆,需要多长呢?1m,2m,8m 还是 25m?一旦物理特征被决定了,又会出现一些新的问题:信号在串行通信口中一次能传输 1bit,在并行通信口中能传输多位(通常是8或者16bit一次)台式计算机采用串行和并行两重方式与其他外围设备通信,如:调制解调器、鼠标和键盘安装串行的方式通信,而打印机用并行数据传输。所有的电子方面的讨论均围绕的是 bit 是什么意思,接受的消息是否和发出的数据是一样的。这需要命令语言和一个已作为协议的回应。现在多数产品已经有了一个标准的协议,事实上现在大多数公司都这么做以使一种产品能和其他的产品相互通信。调制解调器就属于这个范畴。其他设备用他们自己的方式通信,这就意味着一种产品收到的其他的产品的消息可能会出现乱码。打印机就是这样,它有特别的标准,像打印机控制语言和 PostScript。电脑制造商、娱乐设备系统和其他的电子设备生产商就意识到错综复杂的电缆和连接器会使得即使是专业的技术员在第一次试的时候也很难建立正确的系统连接。当人们买了各种部件准备学着和回忆着要在家里把电脑和娱乐设备装起中北大学 2006 届本科毕业设计说明书第 9 页共 14 页来的时候是极其可怕的。为了使家庭电器使用起来跟人性化,我们需要更好的方式把这些电子设备方便的连接在一起。这就是为什么出现了蓝牙设备的原因。蓝牙基础蓝牙是有一群同意任何电器装备如:电脑、移动电话、键盘、耳机等的电子设备生产商产生的一个标准协议,它有自己的连接方式,没有金属丝,没有电缆,用户也没有任何直接的行为来控制。蓝牙是一个确定的工作在两个层面的标准:它提供一个物理层的标准——蓝牙是一种无线射频标准。它也在物理层之上的层面提供协议,在这里数据要被发送的时候,产品必须确定一次应该发送多少数据,在一次连接中怎么能确定从属设备收到的消息就是发送设备发出的消息。蓝牙特别小组的超过 1000 个的成员公司想在电话,电脑和外围设备之间让蓝牙无线通信代替各式各样的电缆。其他的无线连接方式:现在有多种无线连接方式。一种是用红外线谱来携带消息,红外线要求一种肉眼看不见也说不明白的低频光波。红外线大多用在电视系统的遥控系统中,存在一个红外线数据协会(IrDA),过去大多数用在电脑和外围设备的连接中。在这些电脑和娱乐设备使用红外线的目的和方式中,多数是使用一种数字模式——信号的发射和关闭以及数从一点传送到另一点是非常快速的。红外线通信是非常值得信赖的,而且在一个设备中装上红外设备价格不高,但红外线也有其不足的地方:一、红外线是一种“视线”技术,如:你不得不把遥控器对准电视机或者 DVD 来使它正常工作。二、红外线是一种“点对点”的技术,你可以在台式机和笔记本电脑上传输数据,但不能同时在笔记本和掌上设备上利用红外线传输数据。红外线的这两个特性有时候也是它的优点所在,因为红外线的发射和接收装置要被连接在一条线上,所以在他们之间很少出现干扰信号。点对点的特性也使得消息只能发送到特定的接收者,即使是在满是红外线探测器的房间也可以做到这一点。蓝牙解决方案蓝牙技术有意解决红外线和电缆同步系统的问题。硬件生产商,包括西门子、英特尔、东芝、摩托罗拉和爱立信发明了一种非常小的射频模块来装在电脑、电话机和娱乐电子设备中,从用户的角度来说,蓝牙设备有三个重要的特点:它是中北大学 2006 届本科毕业设计说明书第 10 页共 14 页无线的,当走动的时候,你不需要担心公文包里会出现好多电缆连接你的各种设备,你可以随心设计你的办公室而不必为各种线应该从那里穿过而烦心。它的廉价性,这个问题你根本不必考虑。蓝牙不需要你做什么特别的事情来使它工作。设备会找到其他设备并建立其连接,而用户不需要输入任何东西。蓝牙的工作频率,蓝牙通信的工作频率在 2.45GHz,这个频段被国际社会专门留出来供工业、科学和医疗器械使用(ISM)。你所使用的大多数设备可能已经利用上这个射频带了,婴儿***、车库门的开启器以及新一代的无绳电话都在利用这个 ISM 频带。可以肯定的是蓝牙及这些设备在设计的工程中不会出现与现有的设备形成很大的相互干扰的情况。避免干扰:低能量蓝牙设备为了避免干扰情况的一种方式就是发出功率只有 1 毫瓦的信号。经比较,最消耗能量的蜂窝电话能发射 3 瓦的信号。低能量限制了蓝牙的传输范围大概只有 10m,这样就切断了个人电脑与便携电话或者电视机之间的相互干扰。即使这样低的能耗。你的房间的墙壁也不能阻止蓝牙信号,这样的标准有利于控制在不同房间的多个设备。这么多的蓝牙设备存在于你的房间,你可能会想它们之间会存在相互干扰,但这是不可能的。在下面的文字中,我们来看看这是为什么?避免干扰:跳频几种设备在同一时间使用同一频率是不可能出现的,因为蓝牙使用一种技术一一跳频。在这一技术中,一个设备将在指定的范围内用到 79 个独立的、为经安排选择出来的频道,在有规律的基础上从一个频率变到另一个频率。在蓝牙技术中,信号发生者每秒改变频率 1600 次,这意味着更多的设备能充分地利用一个有限的无线射频光谱段。正因为发生器能自动的使用跳频技术,所以在同一时间两个发生器会使用相同的频率的情况不可能出现。这种技术把蓝牙设备中的便携电话或者婴儿***等会使设备中断的风险降到了最低,因为任何在一特定的频率上的相互干扰只会在一秒内的很微小的一部分时间内发生。当一个蓝牙设备和另一个在一起的时候,一段信息交换将会发生以决定是否他们之间有数据需要共享或者一个设备需要控制另一个设备。用户不需要按一下按纽或发出命令,这段信息交换的过程是自动发生的。一旦发生了上述过程,不播放器加载中，请稍候...
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蓝牙设备怎样工作——通信类外文文献翻译、中英文翻译 中北大学 2006 届本科毕业设计说明书第 1 页共 14 页How Bluetooth WorksChatschik BisdikianThere are lots of different ways that electronic devices can connect to one another.For example:Many puter systems have a CPU unit connected to a mouse, akeyboard...
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