Lesson 1 Analog and Digital Signal

1、专业英语通信类通信类为什么要学习这门课程？为什么要学习这门课程？ 与考研英语特点相似，复试 对读研做科研有帮助，特别是图像处理传输、光通信网络方向等； 对工作有帮助 面临毕业，你的选择面临毕业，你的选择 考研，工作，出国？考研，工作，出国？课程关键词课程关键词 专业基础专业基础&英语基础；英语基础； 专业术语；专业术语； 长难句长难句 翻译翻译circuit周围，巡回，绕行周围，巡回，绕行电路电路bus公共汽车公共汽车总线，母线总线，母线short短的短的短路短路1.1.专业英语的特点专业英语的特点circuit周围，巡回，绕行周围，巡回，绕行电路电路bus公共汽车公共汽车总线，母线总

2、线，母线专业性：体现在它的特殊专业内容和特殊专业专业性：体现在它的特殊专业内容和特殊专业词汇上词汇上灵活性：体现在句子结构和词性的使用上。灵活性：体现在句子结构和词性的使用上。 如英语中的动词有的表示动作，有的表示相对静如英语中的动词有的表示动作，有的表示相对静止的状态。止的状态。short短的短的短路短路（1）TV differs from radio in that it sends and receives pictures.电视与无线电的区别在于电视能够发送和接收图像。电视与无线电的区别在于电视能够发送和接收图像。(表示状态表示状态)（2）These two RF signals ar

3、e arranged to differ by a constant frequency.这两个射频信号用于找出一个固定频率。这两个射频信号用于找出一个固定频率。（表示动作）（表示动作）简明性：用尽可能少的单词来清晰地表达原意简明性：用尽可能少的单词来清晰地表达原意过去分词短语可以取代被动语态关系从句，现在分词可以取过去分词短语可以取代被动语态关系从句，现在分词可以取代主动语态关系从句，如代主动语态关系从句，如 In Britain electricity energy generated in power station is fed to the national Grid.不定式短语用以

4、替换表示目的、功能的从句，如不定式短语用以替换表示目的、功能的从句，如 The function of a fuse is to protect a circuit.常使用动词或名词演化成的形容词常使用动词或名词演化成的形容词(state-of-the-art最先进的最先进的)合成新词多合成新词多名词性词组多名词性词组多缩写使用频繁缩写使用频繁长句多长句多在说明书、手册中广泛使用祈使语句在说明书、手册中广泛使用祈使语句用虚拟语气表达假设或建议用虚拟语气表达假设或建议 (if.,或或surpose.)常用常用It句型结构句型结构被动语态使用频繁被动语态使用频繁 合成新词Signal and Sy

5、stem 信号与系统 Digital Signal Processing 数字信号处理 Electronic Design Automation 电子设计自动化 缩写 LED（Light Emitting Diode 发光二极管） LCD（Liquid Crystal Display 液晶显示器） ATM（Asynchronous Transfer Mode 异步传输模式） WLAN（Wireless Local Area Network无线局域网） PTN (Packet Transport Network 分组传送网） 祈使句 Turn on your computer and monit

6、or. Do not store CF cards in hot ,dusty or humid places.考核方式考核方式 上课内容：上课内容：1、3、4、5单元单元 闭卷：闭卷：100分分 题型：专业词汇题型：专业词汇翻译翻译（英译汉、汉译（英译汉、汉译英）；长难句英）；长难句翻译翻译（英译汉）（英译汉） 成绩构成：平时成绩构成：平时*30%+考试考试*70% 平时成绩由作业、出勤、课堂提问等环平时成绩由作业、出勤、课堂提问等环节给出节给出 考试前不划重点、考点范围，只回答同考试前不划重点、考点范围，只回答同学具体提出的问题学具体提出的问题Lesson 1 Analog and Dig

7、ital Signal专业知识回顾 模拟信号、离散信号、数字信号模拟信号、离散信号、数字信号 数字信号数字信号VSVS模拟信号模拟信号 模数转换模数转换Lesson 1 Analog and Digital Signal How is the sound recorded in the computer? And how is the sound in the computer broadcasted? As everyone knows, vibrating of the substance causes the sound. We often record the sound by com

8、puters, and hear the amplified sound from the radios, computers and other electric devices. Then, how does the sound go into the electric system? And how can the sound in the electric systems be broadcast 播送，广播 vibrating of the substance 物体的震动 amplified 放大的 transformed 传输 analog quantity 模拟量 digital

9、 quantity 数字量 a discrete set of 一组离散的 quantitatively 定量地 occur in nature 在自然界存在Lesson 1 Analog and Digital SignalLesson 1 Analog and Digital Signaltransformed and be heard again? 1. What is an analog quantity-a temperature line An analog quantity is one having continuous values. A digital quantity i

10、s one having a discrete set of values. Most things that can be measured quantitatively occur in nature in analog form. For example, the air temperature changes over a continuous range of values. During a given day,the temperature does not go from, say, 70。to 71。Lesson 1 Analog and Digital Signalinst

11、antaneously; it takes on all the infinite valuesin between. If you graphed the temperature on a typical summer day, you would have a smooth, continuous curve in Fig.1-2. Other examples of analog quantities are time,pressure, distance, and sound, as shown in Fig.1-3. Several kinds of analog signals,

12、as shown in Fig.1-4. Lesson 1 Analog and Digital Signal instantaneously 瞬间 takes on 原意为“占据” it takes on all the infinite values in between. 在这个范围内连续变化。 graphed 绘制图形 curve 曲线Lesson 1 Analog and Digital Signal 2. What is a digital quantity-still a temperatureline Rather than graphing the temperature o

13、n a continuous basis, suppose you just take a temperature reading every hour. Now you havesampled values representing the temperature at discrete points in time (every hour) over a 24-hour period, as indicated in Fig.1-5. You haveeffectively converted an analog quantity to a formthat can now be digi

14、tized by representing each sampled value by a digital code. It is important on a continuous basis 在连续的基础上 sampled values 采样值 in time 及时，准时，这里翻译成定时也可以 indicated 表示 digitized 数字化Lesson 1 Analog and Digital SignalLesson 1 Analog and Digital Signalto realize that Fig.1-5 itself is not the digital repres

15、entation of the analog quantity. Each value represented by a dot can be digitized by representing it as a digital code thatconsists of a series of 1s an 0s. Digital representation has certain advantagesover analog representation in electronics applications. For one thing, digital data can be process

16、ed and transmitted more efficiently and reliably than analog data. Also, digital data has a great advantage when storage is necessary. consists of 由组成 has certain advantages over 有一定的优势 applications 应用 processed 处理 transmitted 传输 efficiently 有效地 efficiency 有效性 reliably 可靠地 reliability 可靠性Lesson 1 An

17、alog and Digital SignalLesson 1 Analog and Digital SignalFor example, music when converted to digital form can be stored more compactly and reproduced with greater accuracy and clarity than is possible when it is in analog form. Noise(unwanted voltage fluctuations) does not affectdigital data nearly

18、 as much as it does analog signals. Several kinds of digital signals, as shown in Fig.1-6. music when converted to digital form can be stored more compactly and reproduced with greater accuracy and clarity than is possible when it is in analog form.Lesson 1 Analog and Digital Signal 相对于模拟形式，如果我们把音乐转

19、换成数字形式，存储的时候可以更好地压缩，而且重现声音时，也更加精确和清晰。back fluctuations 波动Noise (unwanted voltage fluctuations) does not affect digital data nearly as much as it does analog signals.notnearly as much as 远远不如数字信号受到的噪声影响远远不如模拟信号大。backLesson 1 Analog and Digital SignalLesson 1 Analog and Digital Signal3. An example of

20、analog system-a speaker A public address system, used to amplify sound so that it can be heard by a large audience, is one simple example of an application of analog electronics. The basic diagram in Fig.1-8 illustrates that sound waves,which are analog in nature, are picked up by amicrophone and co

21、nverted to a small analog voltage called the audio signal. This voltage varies continuously as the volume and frequency of the sound changes and is applied address 讲话，这里翻译为广播 A public address system 公共广播系统 audience 听众 illustrates 说明 picked up 采集 voltage 电压 audio signal 音频信号 volume 音量 frequency 频率Les

22、son 1 Analog and Digital SignalLesson 1 Analog and Digital Signalto the input of a linear amplifier. The output of the amplifier, which is an increased reproductionof input voltage, goes to the speaker (s). The speaker changes the amplified audio signal back to sound waves that have a much greater v

23、olumethan the original sound waves picked up by the microphone. 4. An example of analog and digital system-also a speaker The basic block diagram in Fig.1-9 illustratesa system using digital and analog methods. next a linear amplifier 线性放大器 an increased reproduction of input voltage 输入电压的放大量 origina

24、l 原始的，最初的 block diagram 框图Lesson 1 Analog and Digital SignalLesson 1 Analog and Digital Signal The compact disk (CD) player is an example of a system in which both digital and analog circuits are used. The simplified block diagram inFig.1-9 illustrates the basic principle. Music in digital form is stored on the compact disk. A la