外文翻译--通信系统简介

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1、Introduction to Communication SystemIt is often said that we are living in the information age. Communication technology is absolutely vital to the generation, storage, and transmission of this information.Any communication system moves information from a source to a destination through a channel. F

2、igure 1 illustrates this very simple idea. The information from the source will generally not be in a form that can travel through the channel, so a device called a transmitter will be employed at one end and a receiver at the other.SourceTransmitterReceiverDestinationFigure 1 simple communication s

3、ystemThe source or information signal can be analog or digital. Common examples are analog audio, video signals and digital data. Sources are often described in terms of the frequency range that they occupy. Telephone-quality analog voice signals, for instance, contain frequencies from 300Hz to 3kHz

4、, while analog high-fidelity music needs a frequency range of approximately 20Hz to 20kHz.Digital sources can be derived from audio or video signals can have almost any bandwidth depending on the number of bits transmitted per second, and the method used to convert binary ones and zeros into electri

5、cal signals.A communication channel can be almost anything: a pair of conductors, an optical fiber or a free space that we live. Sometimes a channel can carry the information signal directly. For example, an audio signal can be carried directly by a twisted-pair telephone cable. On the other hand, a

6、 radio link through free space cannot be used directly for voice signals. Such situation require the use of a carrier wave will be altered, or modulated m, by the information signals in such a way that the information can be recovered at the destination. When a carrier is used, the information signa

7、l is also known as the modulating signals.Technology is at the core of many new and emerging digital information products and applications that support the information society. Such products and applications often require the collection, sometimes in real time. The ability of technology to handle re

8、al world signals digitally has made it possible to create affordable, innovative; and high quality products and applications for large consumer market for example: digital cellular mobile phone, digital television and video games. The impact of is also evident in many other areas, such as medicine a

9、nd healthcare. For example: in patient monitors for intensive care, digital X-ray appliances, advanced cardiology and brain mapping systems and so on, digital audio, for example: CD players; audio mixers and electronic music and so on. And personal computer systems for example: disks for efficient d

10、ata storage and error correction, moderns, sound cards and video conferencing and so on. Most of the major cities in the domestic bus stop artificial voice. Every one of the key points from the driver or attendant to stop by voice. But sometimes due to various factors such as weather, vehicle conges

11、tion, flight attendants are feeling the effects of the changes. There being given the stations reporting stations, especially for passengers not familiar with the topography of the city, causing a lot of unnecessary trouble. Well thus affect the image of a city construction window, then developed au

12、tomatic stop system inevitable. As required before the docking system bus GPS information (latitude and longitude information, etc.), longitude and latitude information generated by the distance between bus stops with the message that this is going to experience the tedious, use the micro-controller

13、 difficult to achieve, and when using chips, the proper solution of this problem. Using radians per second in the mathematics dealing with modulation makes the equation simpler. Of course, frequency is usually given in hertz, rather than in radians per second, when practical devices are being discus

14、sed. It is easy to convert between the two systems per second, when practical devices are being discussed. It is easy to convert between the two systems by recalling from basic AC theory, =2f.In modulation, the parameters that can be changed are amplitude E, frequency , and phase . Combinations are

15、also possible. For example, many schemes for transmitting digital information use both amplitude and phase modulation.Multiplexing is the term used in communications to refer to the combining of two or more information signals. When the available frequency range is divided among the signals, the pro

16、cess is known as frequency-division multiplexing (FDM).Radio and television broadcasting, in which the available spectrum is divided among many signals, are everyday examples of FDM. There are limitations to the number of signals that can be crowded into a given frequency range because each requires

17、 a certain bandwidth, For example, a television channel only occupies s given bandwidth of 6MHz in 68MHz bandwidth of VHF.Parallel DSP chip to enhance the performance of a traditional improved through the use of multiply-add units and the Harvard structure, it goes far beyond the computational capab

18、ilities of the traditional microprocessor. A reasonable inference is: chip operations by increasing the number of modules and the corresponding number of bus linking computational modules. The chip can be doubled to enhance the overall operational capacity. Of course, such an inference two precondit

19、ions must be met : First, the memory bus bandwidth as necessary to meet the increase in the number of enhanced data throughput; In addition, various functional units involved in the parallel scheduling algorithm is its complexity can be achieved. An alternative method for using a single communicatio

20、n channel to send many signals is to use time-division multiplexing (TDM). Instead of dividing the available bandwidth of the channel among many signals, the entire bandwidth is used for each signal, but only for a small part of the time. A nonelectronic example is the division of the total availabl

21、e time on a television channel among the various programs transmitted. Each program uses the whole bandwidth of the channel, but only for part of the time.It is certainly possible to combine FDM and TDM, For example, the available bandwidth of a communication satellite is divided among a number of t

22、ransmitter-receiver combinations called transponders. This is an example of FDM. A single transponder can be used to carry a large number of digital signals using TDM.This course presents a top-down approach to communications system design. The course will cover communication theory, algorithms and

23、implementation architectures for essential blocks in modern physical-layer communication systems (coders and decoders, filters, multi-tone modulation, synchronization sub-systems). The course is hands-on, with a project component serving as a vehicle for study of different communication techniques,

24、architectures and implementations. This year, the project is focused on WLAN transceivers. At the end of the course, students will have gone through the complete WLAN System-On-a-Chip design process, from communication theory, through algorithm and architecture all the way to the synthesized standar

25、d-cell RTL chip representation.通信系统简介人们常说我们正生活在一个信息时代，通信技术对信息的产生，存储与转换有着至关重要的作用。任何通信系统的都是通过信道将信息从信源传送到目的地，图1所示为一个简单的系统。来自信源的信息一般是不能通过信道直接传输的 ，因此在一端要用到被称为是发射机的装置，另一端要用到被称为是接收机的装置。信源 转换器 接收机信宿图1 简单通信系统信号源或信息信号 可以是模拟的或数字的。常见的例子是模拟音频信号、视频信号及数据。信息源常被描述为信号所占用的频率范围，例如，电话质量的语音信号，包含着300 Hz3kHz的频率范围，而模拟高保真音乐信

26、号大概需要20 Hz20kHz的频率范围。数字信号源于音频或视频信号，或由数据组成（如文字和字符）。数字信号可以有任意带宽，这要取决于每秒钟传送的比特数和所采用的将二进制1和0转换成电信号的方法。通信信道可以是任何媒介：一对导体、一条光纤或者是我们生活的自由空间。有时信道可以直接承载信息。例如，语音信号可以直接有一对双绞线电话电缆来承载。另一方面，自由空间无线链路不能直接用于承载语音信号，这就需要使用一个载波信号，它的频率能够使语音信号通过信道传输或传播。载波有信息信号改变或调制，这样信息才能够在接受端被恢复。当使用载波时信息信号被称为调制信号。通信技术是许多新的和正在涌现的支撑信息社会的数字

27、信息产品和应用的核心，这些产品和应用要求收集，分析，传输，显示和存储现实世界的信息，有时候则需要实时实现。通信技术数字化地处理现实世界信息的能力，使得广大的消费市场如：数字蜂窝移动电话，数字电视和视频游戏等等。创造可生产的，新的，高指令的产品和应用成为可能，DSP在其它领域的影响力也十分明显的，例如：医学，健康监护，病人监护，数字X光机，先进的心脏和脑电图系统等等，以及数字音频，例如：CD播放器，音频混频器和电子音乐和个人计算机系统，例如：有效数据存储的磁盘，误差校正，调制解调器，声卡和视频会议等等。当前国内主要大城市的公交车大都采用人工语音报站，即每到一站由司机或者乘务员按语音键来进行报站。

28、但有时由于受到各种因素如雨雪天路滑、车上拥挤、乘务员心情的变化等的影响，会出现报错车站，漏报车站的情况，给乘客特别是不熟悉本市地形的乘客带来了不必要的麻烦，进而会影响到一个城市的窗口形象工程建设，于是开发研制自动报站系统成为必然。系统中由于要求对接收到的公交车GPS定位信息（经纬度信息等）进行处理，由经纬度信息生成站牌与公交车之间的距离信息，这之间会经历繁琐的计算，用一般的微控制器难于实现，而当采用处理芯片时，这一问题就很好解决了。调制在数学上采用弧度单位，能释放流程变得简单。当然，在讨论实际装置时，频率通常用赫兹来表示，而不是用弧度每秒来表示，运用交流基本理论=2f，两者之间很容易转换。调制

29、时，能够改变的参数是幅度E频率和相位。复合调制是可能的，例如，发送数字信息的电路既可以采用幅度调制又可以采用相位调制。多路复用是通信的一个术语，它是指将两个或更多的信息复合在一起调制，当在信号中划分可用频率范围时，这个过程被称为频率复用。无线电和电视广播是我们每天都能够感受到的FDM例子，在许多信号中划分它们的频率，由于每种信号都需要占用一定的带宽，因此，对于有些拥挤在给定频率范围内的信号来说，就要受到限制。例如，一个电视信道在68MHz VHF 带宽内，只给定占用6MHz带宽。数字化技术正在极大地改变着我们的生活和体验。作为数字化技术的基石，数字信号处理技术已经、正在、并且还将在其中扮演一个

30、不可或缺的角色。核心是算法与实现，越来越多的人正在认识、熟悉和使用它。因此，理性地评价通信器件的优缺点，及时了解通信的现状以及发展趋势，正确使用芯片，才有可能真正发挥出DSP的作用。现代数字信号处理器的特点和发展趋势是：通信的发展，必须兼顾3P的因素，即性能 、功耗和价格。总的来说，随着VLSI技术的高速发展，现代通信器件在价格显著下降的同时，仍然保持着性能的不断提升和单位运算量的功耗不断降低。选择单一通信信道发送多个信号的方法是采用时分复用，为取代多信号信道对可用带宽的分割，时分复用的每一路信号占用了整个带宽，但却只占用了很少一部分时间。以一个电视节目为例子，时分复用相当于所发送多个节目对一

31、个电视频道总的占用时间的分割。尽管每个节目占用了信道的整个带宽，但只占用了时间的一部分。将FDM与TDM结合在一起使用是当然可以的，例如。在一些被称为是发送与接收一体化的转发器中划分出可用带宽，就是一个FDM的应用例子，即可以用单一转发器携带大量的TDM数字信号。这当然是一种由上而下的方法，以通信系统的设计This course presents a top-down approach to communications system design.The course will cover communication theory, algorithms and implementation

32、 architectures for essential blocks in modern physical-layer communication systems (coders and decoders, filters, multi-tone modulation, synchronization sub-systems).课程将涵盖通信理论，算法和执行架构至关重要的大厦在现代物理层通信系统（编码器与解码器，过滤器，多音调制，同步个子系统） 。 The course is hands-on, with a project component serving as a vehicle fo

33、r study of different communication techniques, architectures and implementations.该课程的手-对，同一个项目的组成部分，服务作为一种工具的研究不同的通信技术，架构和实施。 This year, the project is focused on WLAN transceivers.今年，该项目的重点是无线局域网收发器。 At the end of the course, students will have gone through the complete WLAN System-On-a-Chip design process, from communication theory, through algorithm and architecture all the way to the synthesized standard-cell RTL chip representation.在结束课程后，学员将经历完整的WLAN系统-对-一-芯片设计过程中，从传播理论，通过算法和体系结构的所有方法合成的标准单元的RTL芯片的代表性。5