礦用隔爆型移動(dòng)變電站低壓保護(hù)系統(tǒng)的設(shè)計(jì)-英文翻譯.doc

英文翻譯資料 學(xué)院（部）： 電氣與信息工程學(xué)院 專業(yè)班級(jí)： 學(xué)生姓名： 2012 年 6 月 1 日0安徽理工大學(xué)畢業(yè)設(shè)計(jì)xDSL Analog Circuits and Signal Processing xDSL refers to different DSL, such as ADSL, HDSL and RADSL. DSL uses ordinary telephone lines to high-bandwidth information into the home and small business enterprise technologies. Traditional telephone business through the twisted-pair families or companies connected with the telephone company. Input devices such as access to telephone voice signal (analog signal), it will be transformed into electrical signals. Because the telephone companys signal has been set to use analog signal transmission, so easily on the phone and exchange of information between the phone company. That is why the need to use a computer modem reasons, so that it will be the value of analog signal and converted to digital signals. DSL will not assume that digital signal and then back into analog signals. Digital signal directly in the form of digital transmission to the computer, which allows phone companies to greater bandwidth to transmit information. At the same time, part of the signal is still analog signal transmission in order to use the phone at the same time. DSL including ADSL, CDSL, DSL Lite, HDSL, IDSL, RADSL, SDSL, UDSL, VDSL, x2/DSL.1. Outline xDSL is a DSL (Digital Subscriber Line) of collectively, that is, digital subscriber line, based on copper telephone lines for transmission of point-to-point transmission medium. DSL technology in the traditional telephone network (POTS) users loops symmetrical support and asymmetric transfer mode, often resolved in the network service providers and end-users among the last mile of transmission bottlenecks. Because of the large number of users has been laying loop, so to make full use of existing resources of copper, twisted-pair copper through the high-speed access has become the minimum cost of doing business delivered the mostrealistic solution for broadband access networks. DSL technology has been a large number of applications, is a very mature technology access. System is mainly composed of xDSL central office equipment (DSLAM-Digital Subscriber Line Access Multiplexer) and customer premise equipment (CPE), from the central office DSLAM access platform, DSL central office card, voice separator, IPC (data convergence device) and so on Composition. As shown, voice separator will be on the line and high-frequency digital audio signal modulation signal separation, and audio signals into the telephone exchange, high-frequency signals into digital modulation DSL access system; DSLAM access platform can be inserted at the same time different DSL access Network cards and cards; central office line cards will be on the signal modulation for digital signal and provides data transfer interface; IPC for DSL access system to provide different WAN interfaces such as ATM, Frame Relay, T1/E1, and so on. These facilities are located in the telephone switch systems in the room. DSL Modem by the user equipment and voice component separator, DSL Modem users on the packet modulation and demodulation and provides data transfer interface.2. DSL modulation techniques DSL technology is the use of the phone system not being used for high-frequency signals to transmit data. DSL use of more advanced modulation techniques. At present, the widely used ADSL modulation technology 3: QAM (quadature amplitude modulation), CAP (carrierless amplitude-phase modulation), DMT (discrete multitone), which the DMT modulation technology ANSI Subcommittee T1E1.4 standardized the development of the country Standard used. However, due to the introduction of the standards will not be long; there are still a considerable number of ADSL products using CAP or QAM modulation. QAM modulation technology to achieve the following methods: sending data bits / symbol encoder has been divided into two (the rate for the original 1 / 2), with a pair of orthogonal modulation weight multiplied,after the summation output. Compared with other modulation, QAM coding has to make full use of bandwidth, and strong anti-noise advantages. QAM for ADSL main problem is how to adapt to different telephone lines between the performances of a larger difference. To obtain a more desirable characteristics of the work, QAM receiver and a transmitter with the same frequency and phase characteristics of the input signal for decoding, QAM receiver to use adaptive equalizer to compensate for the transmission signal distortion produced by, the use of QAMs ADSL systems from the complexity of its adaptive equalizer. CAP is based on QAM modulation technology developed, you can say it is a variant of QAM technology. Enter data into the encoder, encoder within, m-bit input has been mapped for k = 2m different complex symbols An = an + jbn, by the K different symbols constitute plural k-CAP line coding. And an encoded bn respectively, were sent to in-phase and quadrature digital shaping filter, after the summation into the D / A converter, as the final low-pass filter signal sent. CAP technology for ADSL is the main technical difficulties to overcome on the local signal crosstalk interference. General crosstalk can be offset through the use of local or proximal crosstalk equalizer to resolve this problem. DMT modulation technology, the main principle is to band (0-1.104MHZ) divided into 256 by the instructions of orthogonal frequency channel (one for each channel bandwidth occupied by 4KHZ), after a bit of the input signal distribution and caching, will enter data into bits Block, the TCM code for 512 points after the discrete Fourier transform (IDFT) will transform into time-domain signal, then bit block will be converted to 256-QAM characters. Then each bit block add cyclic prefix (for the elimination of ISI), the data conversion module (DA) and send the signal sent to filter channel. On the contrary at the receiving end in order to carry out decoding receive.3. DSL classification Symmetric DSL technology as follows: (1)HDSL (high bit-rate DSL) HDSL is xDSL technology in the most mature one, has been more widely used. The technology can be available to full-duplex twisted-pair copper T1 or E1 transmission way. It features: two pairs of twisted-pair transmission; N 64kbps to support a variety of speeds up to E1 rates. HDSL is an alternative to T1/E1 technology, mainly used to connect digital switches, high-bandwidth video conferencing, distance learning, cellular phone base station to connect, such as the establishment of private networks. And traditional T1/E1 technology, HDSL has the following advantages: lower prices; easy to install, T1/E1 request every 0.9 to 1.8 kilometers on the installation of an amplifier, and HDSL in the 3.6 km distance transmission without amplifiers. (2)SDSL - Single-line DSL, which is one-way version of HDSL, which can provide two-way high-speed variable bit rate connection speeds ranging from 160Kbps to 2.084Mbps. It features: a one-on twisted pair; rate to support multiple T1/E1; users based on the data flow, to choose the most appropriate rate of the economy, the rate of up to E1, HDSL than saving a pair of copper wire; 0.4 mm twisted pair of the largest transmission distance of 3 km. (3)MVL-Multiple Virtual Line, its characteristics are as follows: use a pair of twisted-pair; easy to install, inexpensive; low-power, high-density can be installed; the use of ISDN technology with the same frequency, the same cable signal interference with other Very small; support the transmission of voice, no voice in the client separator; support at the same time on the same line to connect up to 8 MVL user equipment, dynamic bandwidth allocation; up / down-sharing rate of up to 768Kbps; transmission distance of up to 7 km. (2) Asymmetric DSL TechnologyAsymmetric DSL technology as follows: 1)ADSL - Asymmetric DSL (asymmetric DSL), ADSL networks to speed up the flow from the 1M and 8M down the traffic, at the same time with an online offer voice telephone services. Characterized by: a pair of twisted-pair transmission; up from the rate of up to 1M, down as much as 8M; at the same time support the transmission of data and voice. 2)RADSL - Rate Adaptive DSL (rate adaptive DSL), this technology allows service providers to adjust bandwidth xDSL connections in order to meet the actual needs and solve quality problems and long lines. Its characteristics are as follows: use a pair of twisted-pair transmission; support synchronous and asynchronous transfer mode; adaptive rate, down from a rate of 640Kbps to 12Mbps, up from the rate of 128Kbps to 1Mbps; at the same time support the transmission of data and voice. 3)VDSL - Very High Data Rate DSL, VDSL and ADSL systems, can make use of ordinary copper telephone without affecting the narrow-band voice services (POTS, ISDN), high-speed data transmission business. VDSL system and structure is very similar to ADSL. VDSL used in a wide spectrum, up to 12MHz. The scope of the spectrum can be divided into a number of downstream (DS) and upstream (US) band, the band commonly used in international division of the way (Band Plan), there are mainly two: Plan 997, Plan 998. Plan998 under the North American division of business needs, mainly business-oriented asymmetric; Plan997 and according to business needs into Europe, mainly business-oriented symmetric. ADSL as a result of the use of spectrum to only the highest 1.1MHz, comparison, VDSL can provide higher transmission speed, more flexibility for different business needs to provide different transmission capacity (of course, transmission distance generally shorter than ADSL) . VDSL application environment can be divided into three categories: (a) short-range high-speed asymmetric operations, for example, less than 300m, downlink transmission rate 26Mb / s and above can be mainly used for video transmission; (b)distance in symmetrical or asymmetrical close to the business For example, about 1km symmetry 10Mb / s; (c) asymmetric long distance business, this time as a result of high-frequency attenuation part of the larger, lower rate up. VDSL technology best suited to users in a relatively intensive, short copper areas, to provide high-speed data access business, so in the East Asian countries (such as South Korea, Japan) to promote the application of constant, in our country have been equipment manufacturers and operators The concern is to promote stage.4. xDSL technology application 1)Symmetric DSL technology Symmetric DSL technology used to replace traditional T1/E1 access technology, and traditional T1/E1 access compared to, DSL technology has a line of low-quality, simple installation and so on. Widely used in communications, network interconnection, and other areas of campus, through the technique, can send multiple voice, video and data. 2)Asymmetric DSL Technology Asymmetric DSL technology is ideal for two-way bandwidth requirements of different applications such as Web browsing, multimedia-on-demand, information dissemination, it is applied to Internet access, VOD system.3xDSL模擬電路和信號(hào)處理xDSL指的是不同的DSL，如ADSL、HDSL和RADSL。DSL是用普通電話線將高帶寬信息帶進(jìn)家庭和小型商業(yè)企業(yè)的技術(shù)。傳統(tǒng)電話業(yè)務(wù)通過(guò)雙絞線將家庭或公司與電話公司相連。輸入設(shè)備如電話機(jī)獲得聲音信號(hào)(為模擬信號(hào))，將它轉(zhuǎn)變?yōu)殡娦盘?hào)。因?yàn)殡娫捁镜男盘?hào)已經(jīng)設(shè)置成使用模擬信號(hào)傳輸，所以很容易在電話和電話公司之間交換信息。這就是為什么計(jì)算機(jī)需要使用調(diào)制解調(diào)器的原因，使它能夠獲得模擬信號(hào)并按值轉(zhuǎn)換為數(shù)字信號(hào)。DSL假定不用將數(shù)字信號(hào)再變回模擬信號(hào)。數(shù)字信號(hào)直接以數(shù)字的形式傳輸?shù)接?jì)算機(jī)，這就使得電話公司能夠以更大的帶寬來(lái)傳輸信息。同時(shí)一部分信號(hào)仍然是模擬信號(hào)傳輸，以便使于同時(shí)使用電話。DSL包括ADSL、CDSL、DSL Lite、HDSL、IDSL、RADSL、SDSL、UDSL、VDSL、x2/DSL。1概述xDSL是DSL(Digital Subscriber Line)的統(tǒng)稱，即數(shù)字用戶線路，是以銅電話線為傳輸介質(zhì)的點(diǎn)對(duì)點(diǎn)傳輸技術(shù)。DSL技術(shù)在傳統(tǒng)的電話網(wǎng)絡(luò)(POTS)的用戶環(huán)路上支持對(duì)稱和非對(duì)稱傳輸模式，解決了經(jīng)常發(fā)生在網(wǎng)絡(luò)服務(wù)供應(yīng)商和最終用戶間的“最后一公里”的傳輸瓶頸問(wèn)題。由于電話用戶環(huán)路已經(jīng)被大量鋪設(shè)，因此充分利用現(xiàn)有的銅纜資源，通過(guò)銅質(zhì)雙絞線實(shí)現(xiàn)高速接入就成為運(yùn)營(yíng)商成本最小最現(xiàn)實(shí)的寬帶接入網(wǎng)解決方案。DSL技術(shù)目前已經(jīng)得到大量應(yīng)用，是非常成熟的接入技術(shù)。xDSL系統(tǒng)主要由局端設(shè)備(DSLAMDigital Subscriber Line Access Multiplexer)和用戶端設(shè)備(CPE)組成，局端由DSLAM接入平臺(tái)、DSL局端卡、語(yǔ)音分離器、IPC(數(shù)據(jù)匯聚設(shè)備)等組成。語(yǔ)音分離器將線路上的音頻信號(hào)和高頻數(shù)字調(diào)制信號(hào)分離，并將音頻信號(hào)送入電話交換機(jī)，高頻數(shù)字調(diào)制信號(hào)送入DSL接入系統(tǒng)；DSLAM接入平臺(tái)可以同時(shí)插入不同的DSL接入卡和網(wǎng)管卡等；局端卡將線路上的信號(hào)調(diào)制為數(shù)字信號(hào)，并提供數(shù)據(jù)傳輸接口；IPC為DSL接入系統(tǒng)提供不同的廣域網(wǎng)接口，如ATM、幀中繼、T1/E1等。這些設(shè)備都設(shè)在電話系統(tǒng)的交換機(jī)房中。用戶設(shè)備由DSL Modem和語(yǔ)音分離器組成，DSL Modem對(duì)用戶的數(shù)據(jù)包進(jìn)行調(diào)制和解調(diào)，并提供數(shù)據(jù)傳輸接口。2DSL調(diào)制技術(shù) DSL技術(shù)是利用在電話系統(tǒng)中沒(méi)有被利用的高頻信號(hào)傳輸數(shù)據(jù)。DSL利用了更加先進(jìn)的調(diào)制技術(shù)。目前被廣泛采用的ADSL調(diào)制技術(shù)有3種：QAM(quadature ampli-tude modulation)、CAP(carrierless amplitude-phase modulation)、DMT(discrete multitone)，其中DMT調(diào)制技術(shù)被ANSI標(biāo)準(zhǔn)化小組T1E1.4制訂的國(guó)家標(biāo)準(zhǔn)所采用。但由于此項(xiàng)標(biāo)準(zhǔn)推出時(shí)間不長(zhǎng)，目前仍有相當(dāng)數(shù)量的ADSL產(chǎn)品采用QAM或CAP調(diào)制技術(shù)。QAM調(diào)制技術(shù)的實(shí)現(xiàn)方法如下：發(fā)送數(shù)據(jù)在比特/符號(hào)編碼器內(nèi)被分成兩路(速率各為原來(lái)的1/2)，分別與一對(duì)正交調(diào)制分量相乘，求和后輸出。與其它調(diào)制技術(shù)相比，QAM編碼具有能充分利用帶寬、抗噪聲能力強(qiáng)等優(yōu)點(diǎn)。QAM 用于ADSL的主要問(wèn)題是如何適應(yīng)不同電話線路之間性能較大的差異性。要取得較為理想的工作特性，QAM接收器需要一個(gè)和發(fā)送端具有相同的頻譜和相位特性的輸入信號(hào)用于解碼，QAM接收器利用自適應(yīng)均衡器來(lái)補(bǔ)償傳輸過(guò)程中信號(hào)產(chǎn)生的失真，因此采用QAM的ADSL系統(tǒng)的復(fù)雜性主要來(lái)自于它的自適應(yīng)均衡器。CAP調(diào)制技術(shù)是以QAM調(diào)制技術(shù)為基礎(chǔ)發(fā)展而來(lái)的，可以說(shuō)它是QAM技術(shù)的一個(gè)變種。輸入數(shù)據(jù)被送入編碼器，在編碼器內(nèi)，m位輸入比特被映射為k2m個(gè)不同的復(fù)數(shù)符號(hào)An = an + jbn，由K個(gè)不同的復(fù)數(shù)符號(hào)構(gòu)成k-CAP線路編碼。編碼后an和bn被分別送入同相和正交數(shù)字整形濾波器，求和后送入D/A轉(zhuǎn)換器，最后經(jīng)低通濾波器信號(hào)發(fā)送出去。CAP技術(shù)用于ADSL的主要技術(shù)難點(diǎn)是要克服近端串音對(duì)信號(hào)的干擾。一般可通過(guò)使用近端串音抵消器或近端串音均衡器來(lái)解決這一問(wèn)題。DMT調(diào)制技術(shù)的主要原理是將頻帶(0-1.104MHZ)分割為256個(gè)由頻率指示的正交子信道（每個(gè)子信道占用4KHZ帶寬），輸入信號(hào)經(jīng)過(guò)比特分配和緩存，將輸入數(shù)據(jù)劃分為比特塊，經(jīng)TCM編碼后再進(jìn)行512點(diǎn)離散傅利葉反變換(IDFT)將信號(hào)變換到時(shí)域，這時(shí)比特塊將轉(zhuǎn)換成256個(gè)QAM子字符。隨后對(duì)每個(gè)比特塊加上循環(huán)前綴（用于消除碼間干擾），經(jīng)數(shù)據(jù)模變換(DA)和發(fā)送濾波器將信號(hào)送上信道。在接收端則按相反的次序進(jìn)行接收解碼。 3DSL分類 對(duì)稱DSL技術(shù)主要有以下幾種：1）HDSL(高比特率DSL)，HDSL是xDSL技術(shù)中最成熟的一種，已經(jīng)得到了較為廣泛的應(yīng)用。這種技術(shù)可以通過(guò)現(xiàn)有的銅雙絞線以全雙工T1或E1方式傳輸。其特點(diǎn)是：利用兩對(duì)雙絞線傳輸；支持N64kbps各種速率，最高可達(dá)E1速率。HDSL是T1/E1的一種替代技術(shù)，主要用于數(shù)字交換機(jī)的連接、高帶寬視頻會(huì)議、遠(yuǎn)程教學(xué)、蜂窩電話基站連接、專用網(wǎng)絡(luò)建立等。與傳統(tǒng)的T1/E1技術(shù)相比，HDSL具有以下優(yōu)點(diǎn)：價(jià)格便宜；容易安裝，T1/E1要求每隔0.91.8公里就安裝一個(gè)放大器，而HDSL可