UNIT 12 Real World Signal Processing,12.1 Text Analog to Digital and Digital to Analog Conversion A/D和D/A转换,New Words potentiometer pu,tenimit n. 电位计，分压计 digitize diditaiz v. 将数字化 predefine pri:difain v. 预定义 quantize kwntaiz v. 量化 increment inkrimnt n. 增加，增量 acquisition ,kwizin n. 获取，采集，探测 imperfect imp:fikt a.; n. 半完成的，减弱的；未完成体,Exercises 1. Answer the following questions. A/D and D/A converters are used to interface a digital-computer-based industrial controller with analog device. On the input side of a computer, a measurement process provides an electric signal in analog form. Signals that drive actuators on the output side are controlled by binary digital outputs. The full range of the device is 05 volts. The input binary count can range between 0210. Since there are 210-1=1024-1=1023 increments over the full range of the 5-0=5 volts, the step size of the 10-bit D/A converter is 5/1023=0.00489 volts. This is accomplished by sampling the analog input at discrete intervals of time and mapping each sample into one of the discrete quantizing levels. An A/D converter has 2n discrete quantizing levels, where n is the number of bits in the register of the A/D converter. In the case of the 10-bit A/D converter, the percent resolution can be computed using equation (12-2). Accuracy and linearity errors are in addition to resolution inaccuracies.,Exercises (continue) 2. According to the text, fill in the blanks with suitable words and values given below in the correct form. number digital A/D analog amplify sampling quantizing encoding 0.75 8 map sample level practical largest ideal scale conditioning store degree actual resolution discrete (1) number (2) digital A/D analog sampling quantizing encoding (3) 8 (4) 0.75 (5) samples discrete maps level (6) largest practical ideal (7) degree stored actual resolution (8) scale amplified conditioning,12.2 Reading and Translation Digital Signal Processing 数字信号处理,New Words ingredient inri:dint n. 成分，因素 frame freim n. 帧，换面 physiology ,fizildi n. 生理学，生理机能 ecological ,i:kldikl a. 生态的，生态学的 operator preit n. 算子 GPS abbr. 全球定位系统（global positioning system） transmitter trnsmit n. 发送器，发射机 receiver risi:v n. 接收器，接受者 modulation ,mdjulein n. 调制，调节 exclusively iksklu:sivli ad. 排外地，专有地 FFT abbr. 快速傅里叶变换（fast Fourier transform） staircase stkeis n. 阶梯,Notes signal conditioning 信号调节，信号调理，信号波形加工,斜体部分参考译文: For example, a black-and-white picture is a representation of light intensity as a function of two spatial coordinates; a video signal in television consists of a sequence of images, called frames, and is a function of three independent variables that are spatial coordinates and time. 例如，一张黑白照片记录了光的强度，它是二维空间坐标变量的一个函数；一个电视视频信号是由一系列被称为帧的图像组成的，它是关于空间坐标变量和时间变量的三个独立变量的函数。 Functionally, the transmitter changes the message signal into a form suitable for transmission over the channel, the channel is the physical medium that connects the transmitter and receiver, and the receiver processes the channel output to produce an estimate of the message signal for a user. 从功能上来说，发送器把报文（message）信号转化为适合在信道中传输的形式；而信道是连接发送器和接收器的物理媒体；接收器对信道的输出进行处理得到有用的信号以供用户使用。 The rapid development of digital computers and microprocessors together with some important theoretical progress such as the fast Fourier transform (FFT) algorithm caused a major shift to digital technologies, giving rise to the field of digital signal processing. 随着计算机和微处理器的快速发展，以及诸如快速傅里叶变换（Fast Fourier Transform, FFT）这些理论上取得的重大进步，人们转而大量地使用数字技术，从而产生了数字信号处理这一领域 。,斜体部分参考译文(续): Primarily due to the above advantages, DSP is now becoming a first choice in many technologies and applications, such as consumer electronics, communications, wireless telephones, and medical images. 由于具有以上优点，如今，DSP已经成为许多技术和应用中的第一选择，诸如消费电子产品、通信、无线电话以及医学图像处理技术。,12.3 Further Reading Smart Sensors and Actuators 智能传感器与执行器,New Words entity entti n. 实体 lag l n. 延迟；滞后 node nud n. 节点 align lain v. 匹配；对齐 bounce bauns n. 颤动，跳动 encapsulate inkpsleit v. 封装 fieldbus fi:ldbs n. 现场总线,1. 英文书信的种类 英文书信大致可分为私人信件（private letter）和事务信件（business letter）两大类。私人信件又称为非正式信件（informal letter），事务信件一般是正式信件（formal letter）。值得注意的是，给陌生人或重要的人写信也要使用正式信件。,12.4 General Knowledge 英文书信 书信（letter）是书面语言，它是我们进行友好交往，贸易往来，交流情况，沟通思想，增进友谊的主要途径。任何一封简单的书信，不仅能反映出写信人的思想认识、文化水平和处事态度，而且会给人们一种深刻的印象和影响，尤其是涉外书信。,2. 信封的格式 英文信封（envelope）的书写格式与中文信封不尽相同，或者说完全不同。英文信封由三个主要部分构成，发信人的姓名、地址（或单位名称）放在信封的左上角，收信人的姓名、地址（或单位名称）则通常居中，邮票（stamp）置于信封的右上角，图12-8给出了一个信封书写格式实例。,3. 信笺的格式 如图12-9所示，信笺一般由下列七个部分组成。,科技论文的结构与写作（续）,4. 附言与附件 附言：一般而言，除非确属需要，最好不要附言，尤其郑重的函件，更应避免。若确实需要，则在签名的下一、二行，信笺的左边，先写P.S.（即Postscript的缩写），接着写出要讲的话。 附件：如果正文内已说明有附件要寄，那么要在信笺的左下角附注说明，以便收信人查阅。,课后作业 P.116，Exercise 3,