外文翻譯--通信系統(tǒng)簡(jiǎn)介-精品

1、Introduction to Communication SystemIt is ofte n said that we are living in the in formatio n age. Communi cati on tech no logy is absolutely vital to the gen erati on, storage, and tran smissi on of this in formatio n.Any com muni cati on system moves in formatio n from a source to a dest in ati on

2、 through a cha nn el. Figure 1 illustrates this very simple idea. The in formatio n from the source will gen erally n ot 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.Figure 1 simple com muni catio n systemT

3、he source or in formatio n sig nal can be an alog or digital. Com mon examples are an alog audio, video signals and digital data. Sources are often described in terms of the frequency range that they occupy. Telepho ne-quality an alog voice sig nals, for in sta nee, contain freque ncies from 300Hz t

4、o 3kHz, while an alog high-fidelity music n eeds a freque ncy range of approximately 20Hz to 20kHz.Digital sources can be derived from audio or video sig nals can have almost any ban dwidth depe nding on the nu mber of bits tran smitted per sec ond, and the method used to convert binary ones and zer

5、os into electrical sig nals.A com muni cati on cha nnel can be almost anything: a pair of con ductors, 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 teleph one cable

6、. On the other hand, a 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,

7、 the information signal is also known as the modulating signals.Tech no logy is at the core of many new and emerg ing digital in formati on products and applicati ons that support the information society. Such products and applications often require the collection, sometimes in real time. The abilit

8、y of tech no logy to han dle real world sig nals digitally has made it possible to create affordable, inno vative; and high quality products and applicati ons for large con sumer market for example: digital cellular mobile pho ne, digital televisi on and video games. The impact of is also evide nt i

9、n many other areas, such as medicine and healthcare. For example: in patient monitors for intensive care, digital X-ray appliances, advaneed cardiology and brain mapping systems and so on, digital audio, for example: CD players; audio mixers and electro nic music and so on. And pers onal computer sy

10、stems for example: disks for efficie nt data storage and error correct ion, moder ns, 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 atte ndant to stop by voice. But sometimes due to vari

11、ous factors such as weather, vehicle con gesti on, flight attendants are feeling the effects of the changes. There being given the station's reporting stations, especially for passengers not familiar with the topography of the city, causing a lot of unnecessary trouble. Well thus affect the imag

12、e of a city construction window, then developed automatic 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 t

13、o experience the tedious, use the micro-controller 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 pe

14、r second, when practical devices are being discussed. It is easy to convert between the two systems per second, when practical devices are being discussed. It is easy to convert betwee n the two systems by recalli ng from basic AC theory, w =2 nIn modulation, the parameters that can be changed are a

15、mplitude E, frequency w, and phase 0 . Combinations are 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 availab

16、le frequency range is divided among the signals, the process 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 cr

17、owded into a given frequency range because each requires 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 Harva

18、rd structure, it goes far beyond the computational capabilities 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 operatio

19、nal capacity. Of course, such an inference two preconditions 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 achieve

20、d.An alternative method for using a single communication 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 none

21、lectronic example is the division of the total available 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

22、 communication satellite is divided among a number of transmitter-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

23、course will cover communication theory, algorithms and 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 ve

24、hicle for study of different communication techniques, 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

25、and architecture all the way to the synthesized standard-cell RTL chip representation.通信系統(tǒng)簡(jiǎn)介人們常說我們正生活在一個(gè)信息時(shí)代，通信技術(shù)對(duì)信息的產(chǎn)生，存儲(chǔ)與轉(zhuǎn)換有著至關(guān)重要的作用。任何通信系統(tǒng)的都是通過信道將信息從信源傳送到目的地，圖1所示為一個(gè)簡(jiǎn)單的系統(tǒng)。 來自信源的信息一般是不能通過信道直接傳輸?shù)?，因此在一端要用到被稱為是發(fā)射機(jī)的裝置，另一端要用到被稱為是接收機(jī)的裝置。圖1簡(jiǎn)單通信系統(tǒng)信號(hào)源或信息信號(hào) 可以是模擬的或數(shù)字的。常見的例子是模擬音頻信號(hào)、視頻信號(hào)及數(shù)據(jù)。信息源常被描述為信號(hào)所占用的頻率范圍

26、，例如，電話質(zhì)量的語音信號(hào)，包含著300 Hz3kHz的頻率范圍，而模擬高保真音樂信號(hào)大概需要20 Hz20kHz的頻率范圍。數(shù)字信號(hào)源于音頻或視頻信號(hào)，或由數(shù)據(jù)組成（如文字和字符）。數(shù)字信號(hào)可以有任意帶寬，這要取決于每秒鐘傳送的比特?cái)?shù)和所采用的將二進(jìn)制1和0轉(zhuǎn)換成電信號(hào)的方法。通信信道可以是任何媒介： 一對(duì)導(dǎo)體、一條光纖或者是我們生活的自由空間。有時(shí)信道可以直接承載信息。例如，語音信號(hào)可以直接有一對(duì)雙絞線電話電纜來承載。另一方面，自由空間無線鏈路不能直 接用于承載語音信號(hào)，這就需要使用一個(gè)載波信號(hào)，它的頻率能夠使語音信號(hào)通過信道傳輸或傳播。載波有信息信號(hào)改變或調(diào)制，這樣信息才能夠在接受端被恢

27、復(fù)。當(dāng)使用載波時(shí)信息信號(hào)被稱為調(diào)制信號(hào)。通信技術(shù)是許多新的和正在涌現(xiàn)的支撐信息社會(huì)的數(shù)字信息產(chǎn)品和應(yīng)用的核心，這些產(chǎn)品和應(yīng)用要求收集，分析，傳輸，顯示和存儲(chǔ)現(xiàn)實(shí)世界的信息，有時(shí)候則需要實(shí)時(shí)實(shí)現(xiàn)。通信技術(shù)數(shù)字化地處理現(xiàn) 實(shí)世界信息的能力，使得廣大的消費(fèi)市場(chǎng)如：數(shù)字蜂窩移動(dòng)電話，數(shù)字電視和視頻游戲等等。創(chuàng)造可生 產(chǎn)的，新的，高指令的產(chǎn)品和應(yīng)用成為可能，DSP在其它領(lǐng)域的影響力也十分明顯的，例如：醫(yī)學(xué)，健康監(jiān)護(hù)，病人監(jiān)護(hù)，數(shù)字X光機(jī)，先進(jìn)的心臟和腦電圖系統(tǒng)等等，以及數(shù)字音頻，例如：CD播放器，音頻混頻器和電子音樂和個(gè)人計(jì)算機(jī)系統(tǒng)，例如：有效數(shù)據(jù)存儲(chǔ)的磁盤，誤差校正，調(diào)制解調(diào)器，聲卡 和視頻會(huì)議等等。

28、當(dāng)前國(guó)內(nèi)主要大城市的公交車大都采用人工語音報(bào)站，即每到一站由司機(jī)或者乘務(wù)員按語音鍵來進(jìn)行報(bào)站。但有時(shí)由于受到各種因素如雨雪天路滑、車上擁擠、乘務(wù)員心情的變化等的影響，會(huì)出現(xiàn)報(bào)錯(cuò) 車站，漏報(bào)車站的情況，給乘客特別是不熟悉本市地形的乘客帶來了不必要的麻煩，進(jìn)而會(huì)影響到一個(gè)城市的窗口形象工程建設(shè)，于是開發(fā)研制自動(dòng)報(bào)站系統(tǒng)成為必然。系統(tǒng)中由于要求對(duì)接收到的公交車 GPS定位信息（經(jīng)緯度信息等）進(jìn)行處理，由經(jīng)緯度信息生成站牌與公交車之間的距離信息，這之間 會(huì)經(jīng)歷繁瑣的計(jì)算，用一般的微控制器難于實(shí)現(xiàn)，而當(dāng)采用處理芯片時(shí)，這一問題就很好解決了。調(diào)制在數(shù)學(xué)上采用弧度單位，能釋放流程變得簡(jiǎn)單。當(dāng)然，在討論實(shí)際裝置時(shí)，頻率通常用赫茲來Tan smitter表示，而不是用弧度每秒來表示，運(yùn)用交流基本理論3 =2 n,f兩者之間很容易轉(zhuǎn)換。調(diào)制時(shí)，能夠改變的參數(shù)是幅度E頻率3