英语测控专业英语.pptx
Text tourOutline 4.1 Introduction4.2 Elements of Probability Theory4.3 Amplitude Distribution and Moments4.4 The Autocorrelation and Power Spectral Density 2023/3/261测控技术与仪器英语教程第1页/共44页4.1 IntroductionThe background of random signalsExample about several signalsFigure 4.1 Signal displaying(a)random amplitude,(b)random timing of transition between fixed levels,and(c)random amplitude and timing components in an essentially repetitive waveform.2023/3/262测控技术与仪器英语教程第2页/共44页4.1 IntroductionThe origin of random signal and the way of dealing with it 2023/3/263测控技术与仪器英语教程第3页/共44页4.2 Elements of Probability Theory4.2.1 The probability of an Event4.2.2 Joint and Conditional Probabilities4.2.3 The Probability Density Function2023/3/264测控技术与仪器英语教程第4页/共44页4.2.1 The Probability of an EventUsing examples to define the probability of an eventthe basic additive law of probability =2023/3/265测控技术与仪器英语教程第5页/共44页4.2.2 Joint and Conditional ProbabilitiesThe joint probabilityThe conditional probabilitiesThe Bayes rule,relates the conditional probability of A given B to that of B given A.2023/3/266测控技术与仪器英语教程第6页/共44页4.2.2 Joint and conditional probabilitiesThe statistically independentThe joint and conditional probabilities relevance to signals and signal analysis Figure 4.2(a)A portion of a random sampled-data signal with six discrete levels and(b)the probabilities associated with each level2023/3/267测控技术与仪器英语教程第7页/共44页4.2.3 The Probability Density Functionthe probability density function Figure 4.3 A continuous random signal2023/3/268测控技术与仪器英语教程第8页/共44页4.2.3 The Probability Density FunctionExample2023/3/269测控技术与仪器英语教程第9页/共44页 4.3 Amplitude Distribution and Momentsamplitude distributions:)deterministic signals 2023/3/2610测控技术与仪器英语教程第10页/共44页4.3 Amplitude Distribution and Moments )the amplitude distribution of a signal tells us nothing about its detailed structure or spectrum,nor is it a unique property of the signal.Figure 4.6 Portions of four waveforms with identical amplitude distributions 2023/3/2611测控技术与仪器英语教程第11页/共44页4.3 Amplitude Distribution and MomentsThe first central moment is also called the expectedThe second central moment is referred to as the standard deviation.2023/3/2612测控技术与仪器英语教程第12页/共44页4.3 Amplitude Distribution and Momentsthe central moments and moments are closely related 2023/3/2613测控技术与仪器英语教程第13页/共44页4.4 The Autocorrelation and Power Spectral Density4.4.1 The Spectral Properties of Random Signals4.4.2 The Autocorrelation Function4.4.3 The Power Spectral Density Function2023/3/2614测控技术与仪器英语教程第14页/共44页4.4.1 The Spectral Properties of Random SignalsThe spectral measure of random signals is very useful Figure 4.72023/3/2615测控技术与仪器英语教程第15页/共44页4.4.2 The Autocorrelation FunctionThe autocorrelation function(ACF)of a signal waveform is an average measure of its time-domain propertiesfinite ACF 2023/3/2616测控技术与仪器英语教程第16页/共44页4.4.2 The Autocorrelation Functionthe shift is equal to a multiple of the sampling interval T some of ACFs principal properties 2023/3/2617测控技术与仪器英语教程第17页/共44页4.4.2 The Autocorrelation FunctionFigure 4.8 (a)A signal with two discrete frequency components,and(b)its autocorrelation function2023/3/2618测控技术与仪器英语教程第18页/共44页4.4.2 The Autocorrelation FunctionThe peak value of ACF is given by 2023/3/2619测控技术与仪器英语教程第19页/共44页4.4.3 The Power Spectral Density Functionpower spectrum,power spectral,density energy spectrum Figure 4.9(a)A signal and its autocorrelation function,and(b)their corresponding frequency-domain descriptions and involves both magnitude and phase terms,whereas is purely real2023/3/2620测控技术与仪器英语教程第20页/共44页4.4.3 The Power Spectral Density FunctionThe relation between the ACF and power spectrum,or power spectral density 2023/3/2621测控技术与仪器英语教程第21页/共44页Language in useVocabulary calculate,transmit,random,convey,obvious,identicalStructureReading/writing techniques2023/3/2622测控技术与仪器英语教程第22页/共44页Vocabulary2023/3/2623测控技术与仪器英语教程第23页/共44页calculate in dictionary计算：通过计算来确认；计算估计：做出估计；估价考虑，设想：为特定目的安排；设计推测：计划、打算或计数2023/3/2624测控技术与仪器英语教程第24页/共44页calculate in textSuch signals are described as deterministic,and the frequency spectra we calculate for them specify the magnitudes and relative phases of the sinusoidal wave which,if add together,would exactly resynthesise the original waveforms.这类信号被描述成“确定性”信号，由它们所得出的频谱详细表述了正弦波的幅值和相对相位，如果将这些正弦波叠加起来就会很精确的合成为原波形。2023/3/2625测控技术与仪器英语教程第25页/共44页calculate in usecalculating the area of a circle;calculated their probable time of arrival.计算圆的面积；计算他们可能的抵达时间calculating the teams chances of winning.估计该队获胜的可能a sturdy car that is calculated to last for years;a choice that was calculated to please.设计能耐用多年的牢固汽车；一项为取悦而设计的选择I callate shes a right smart cook我猜测她是一位手艺精巧的厨师2023/3/2626测控技术与仪器英语教程第26页/共44页transmit in dictionary传送：从一个人、事物或地点传送到另一人、事物或地点；传染：使传播；传染遗传：通过遗留或继承的方式给予或传达给另一个人；传下去传播：传播（消息或信息）；交流传送：通过电线或无线电等传送（信号）传导：在通过一个媒质时产生的（振动）传到：把（力或能量）从机械装置的一个部分传到另一个部分2023/3/2627测控技术与仪器英语教程第27页/共44页transmit in textAs a simple example,it would be pointless to transmit a continuous sinusoidal tone,sine once its amplitude,frequency and phase characteristics have been determined by the receiver,no further information is conveyed.一个简单的例子是，传送一个连续的正弦音是无意义的，因为一旦接收者确定了正弦的振幅、频率和相位特性，就没有进一步的信息传送了。2023/3/2628测控技术与仪器英语教程第28页/共44页transmit in usetransmit an infection.传播传染渍2023/3/2629测控技术与仪器英语教程第29页/共44页random in dictionary没有具体形式、目的或内容的：随机的：同组中每个成员都有相同或平等机会或可能出现的2023/3/2630测控技术与仪器英语教程第30页/共44页random in textA signal may be random in a variety of ways,perhaps the most common type of randomness is in the amplitude of a signal waveform,illustrated in figure 4.1(a).信号的随机性表现在各方面，或许最普遍的随机性是在信号的振幅上，如图4.1(a)所示。2023/3/2631测控技术与仪器英语教程第31页/共44页random in userandom movements;a random choice.随意运动；一个随意的选择2023/3/2632测控技术与仪器英语教程第32页/共44页convey in dictionary传送：将从一个地方运送或输送到另一个地方；输送传播：作为的传送或传播媒介；传播交流或使知道；告知将财产权或头衔转让给2023/3/2633测控技术与仪器英语教程第33页/共44页convey in textno further information is conveyed.没有进一步的信息传送了。2023/3/2634测控技术与仪器英语教程第34页/共44页convey in usewires that convey electricity.传电的金属线a look intended to convey sympathetic comprehension脸上的神情想要传达同情与谅解2023/3/2635测控技术与仪器英语教程第35页/共44页obvious in dictionary明显的：容易感到或理解的；易看透的：因为不精巧而容易被看穿；透明的：挡路的：站在路中或前面的2023/3/2636测控技术与仪器英语教程第36页/共44页obvious in textIt is obvious that if outcome B is completely unaffected by outcome A 显然，如果结果和结果相互完全不影响 2023/3/2637测控技术与仪器英语教程第37页/共44页obvious in usean obvious political ploy.一个易被识破的政治手法2023/3/2638测控技术与仪器英语教程第38页/共44页identical in dictionary同一的：完全相等的或相似的可互换的：十分类似或相象以至于本质上相等的或能互换的同卵双生的：从同一受精卵中产生的，具有相同基因结构和相似外貌的孪生子的；单卵的2023/3/2639测控技术与仪器英语教程第39页/共44页identical in textThese equations are identical in form to the Fourier transform pair which relate a signal f(t)to its spectrum ,expect that we are now working in terms of the delay variable rather than the time variable t.我们使用的是延时变量而不是时间变量的话，通过傅立叶变化和反变换可以把信号f(t)和它的频谱相对应起来，按照傅立叶变换和反变换的形式，这些等式是完全相同的。2023/3/2640测控技术与仪器英语教程第40页/共44页identical in useanother orator who used the senators identical words.另一个发言者使用了与这个参议员完全相同的措词2023/3/2641测控技术与仪器英语教程第41页/共44页Structure2023/3/2642测控技术与仪器英语教程第42页/共44页Reading/writing techniques2023/3/2643测控技术与仪器英语教程第43页/共44页感谢您的观看！第44页/共44页
