专业英语Lesson-3-Sampled-Data-Signals-《测控技术与仪器英语教程》课件.ppt

Lesson 3 Sampled-Data Signals BackgroundsText tour Language in useVocabulary Structure Reading/writing techniques4/10/20231测控技术与仪器英语教程BackgroundsTerminology Digital electronics 数字电子The Dirac function 迪拉克函数Shifting property 移位算子 Time and frequency-domain 时域和频域 Spectral lines 谱线DFT 离散傅里叶变换FFT 快速傅里叶变换Mapping 映射 Decaying oscillatory function 衰减振荡函数 4/10/20232测控技术与仪器英语教程Text tourOutline 3.1 Introduction3.2 Mathematical Description Using the Dirac Function3.3 Spectra of Sampled-data Signals3.4 The z-transform4/10/20233测控技术与仪器英语教程3.1 IntroductionSampled-data signals arise whenever continuous functions are measured or recorded intermittently and the interval between successive samples is sufficiently small 4/10/20234测控技术与仪器英语教程3.2 Mathematical Description Using the Dirac FunctionDiscussing the spectrum of a delayed Dirac pulse which occurs at some instant t=T.Clearly 4/10/20236测控技术与仪器英语教程3.3 Spectra of Sampled-data Signals3.3.1 The Discrete Fourier Transform3.3.2 The Fast Fourier Transform 4/10/20237测控技术与仪器英语教程3.3.1 The Discrete Fourier TransformThe reasons that the Fourier transform of a sampled-data signal is generally referred to as a discrete Fourier transform(DFT)the signal itself is discrete )The Fourier transform can only be estimated for a set of discrete values of The way of visualize the spectrum of a sampled-data signal form 4/10/20238测控技术与仪器英语教程3.3.2 The Fast Fourier TransformThe number of computer operations needed to evaluate the DFT of a signal consisting of N samples.The introduction of the fast Fourier transform(FFT)4/10/202310测控技术与仪器英语教程3.4 The z-transform 3.4.1 Introduction 3.4.2 Z-plane Poles and Zeros 4/10/202311测控技术与仪器英语教程3.4.1 IntroductionExample:4/10/202313测控技术与仪器英语教程3.4.2 Z-plane Poles and ZerosThe time functions corresponding to a few z-transforms Figure 3.3(a)A z-plane pole-zero configuration,(b)the corresponding time function,and(c)the magnitude of its spectrum4/10/202315测控技术与仪器英语教程3.4.2 Z-plane Poles and ZerosFigure 3.4 The effects of removing one of the z-plane zeros of figure 3.3the zero at z=1 is now removed:4/10/202316测控技术与仪器英语教程3.4.2 Z-plane Poles and ZerosA truncated version of the infinite decaying exponential waveform Figure 3.5 Truncated and infinite version of a sampled exponential Signal Consider next the z-transform 4/10/202318测控技术与仪器英语教程3.4.2 Z-plane Poles and ZerosFigure 3.6 z-plane zeros of a sampled exponential signal truncated to 12 terms4/10/202319测控技术与仪器英语教程3.4.2 Z-plane Poles and ZerosA decaying oscillatory function Figure 3.7(a)A pole zero configuration which includes a complex conjugate pole pair just inside the unit circle,and(b)the corresponding time function4/10/202320测控技术与仪器英语教程Language in useVocabulary underlying,refer,trajectory,reinforce,functionStructureReading/writing techniques4/10/202321测控技术与仪器英语教程Vocabulary4/10/202322测控技术与仪器英语教程underlying in textIt should be emphasized from the start that a set of sample values only forms an adequate substitute for the underlying continuous signal waveform if the interval between successive samples is sufficiently small.必须强调的是，这一连串采样值只有当连续采样点间隔足够小时才能充分替代该连续信号波形 4/10/202324测控技术与仪器英语教程underlying in useunderlying strata.下层an underlying meaning.潜在的意义an underlying financial claim.优先的财政要求4/10/202325测控技术与仪器英语教程refer in dictionary引去求助：指点到消息来源处寻求帮助或信息归因于：指派或归因于；认为起源于认为属于：指定或认为属于一种特定的种类或类型遵照：提交（有争议的事件）给权威机构仲裁、决定或检查使注意：引导的注意力：4/10/202326测控技术与仪器英语教程refer in usereferred her to a heart specialist;referred me to his last employer for a recommendation.叫她找心脏病专家；叫我向他以前的雇主查询对他的推荐refer him to his duties.叫他把注意力放到工作上4/10/202328测控技术与仪器英语教程trajectory in dictionary轨迹，弹道：抛射物或其它在空间运动的物体的运动路线道路：选择好的或采用的路径常角轨道，轨线：以同样的角度切割给定系统所有曲线或平面的曲线4/10/202329测控技术与仪器英语教程Trajectory in usea moral trajectory,a style of aspiration 一条道德的道路，一种抱负的时尚4/10/202331测控技术与仪器英语教程reinforce in dictionary增强：给予更多的力量或效力；加强增援：以额外的人员或装备加强部队的力量加强：用增加支持或物资来加强增加：增加的数量；增加强化刺激法：在达到需要的反应或表现后给（例如试验物）一个强化刺激的东西强化刺激：用强化刺激的方法来刺激（一个人）4/10/202332测控技术与仪器英语教程reinforce in textWhen a large number of cosines of similar amplitude but different frequency are added together,they tend to cancel each other out everywhere except at t=0,where they all reinforce.当很多幅值相同而频率不同的余弦分量相加时，它们会在除t=0点外互相抵消，在该点它们会相互增强。4/10/202333测控技术与仪器英语教程reinforce in useThe news reinforced her hopes.这个消息增强了她的希望4/10/202334测控技术与仪器英语教程function in dictionary作用，功能：特别适合某人或某人所从事的行为角色，职业：特定的工作或角色：应变物：与另一决定它的存在、价值或重要性的事物密切相关的事物：应变量，函数：一个与他量有关联的变量，这一量中的任何一值都能在他量中找到对应的固定值4/10/202335测控技术与仪器英语教程function in textThe Dirac function,often referred to as the impulse function,is a pulse of extremely short duration and unit area.迪拉克函数，通常也叫单位脉冲函数，它是一个持续时间极短且具有单位面积的脉冲。4/10/202336测控技术与仪器英语教程function in usein my function as chief editor.在我担任总编辑的职位Growth is a function of nutrition.长身体是由营养决定的4/10/202337测控技术与仪器英语教程Structure4/10/202338测控技术与仪器英语教程Reading/writing techniques4/10/202339测控技术与仪器英语教程