通信和电子信息科技英语总省公共课一等奖全国赛课获奖课件.pptx
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1、Exercises.Please translate the following words and phrases into Chinese.1.sample function2.ensemble average 3.physical significance4.a Fourier transform pair5.deterministic waveform6.in the limit 7.time invariant8.an upperfrequency limit9.Parsevals theorem 10.random pulses样本函数总体均值物理意义傅立叶变换对确定性波型在极限情
2、况下时不变频率上限巴塞瓦尔定理随机脉冲第1页Exercises.Please translate the following words and phrases into English.1.随机过程2.统计平均3.随机变量4.自相关函数5.傅里叶变换6.功率谱密度7.概率密度函数8.高斯过程9.平稳过程10.统计独立random process statistical average random variable autocorrelation function Fourier transform power spectral density probability density fun
3、ction gaussian process a stationary process statistically independent 第2页11.时间平均(值)12.统计特征13.各态历经过程14.狄拉克函数time average statistical characteristic ergodic process delta function 第3页Exercises.Fill in the blanks with the missing word(s).1.The ensemble averages will be identical the statistical average
4、s and may be represented by the same symbols.2.The averages determined by measurements a single sample Function successive times will yield a time average,which we represent as n2(t1).3.Suppose,for example,that the statistical characteristics of the sample Functions the ensemble were changing with t
5、ime.4.For it may happen that while each sample function is stationary the individual sample functions may differ statistically one another.5.As an extension of that result we shall define the power spectral density of a random process the same way.withonatinfromin第4页Exercises6.It is interest to inqu
6、ire whether G(f)defined Eq.(1.2)for a random process has a physical significance whichcorresponds to the physical significance of G(f)for deterministic waveforms.8.Hence,if we should select some sample function,a knowledge of the value of n(t)at time t would be no assistance improving our ability to
7、 predict the value attained by that same sample function at time t+.9.Hence,whenever we make an observation or measurement of the pulse waveform which extends a duration long enough so that the average observed pulse shape,such as their amplitudes,widths,and spacings are representative of the wavefo
8、rm generally,we shall find that Eq.(1.12)applies.ofinofinover第5页Exercises10.Let us select a section of this waveform which extends -T/2 -T/2.11.Since we have assumed an ergodic process,we are at liberty to (perform,performing)the averaging any sample function of the ensemble,since every sample funct
9、ion will yield the same result.tofromperformover第6页.Please translate the following words and phrases into Chinese.1.physical syste2.rise time 3.amount of information 4.in principle 5.gaussian channel 6.probability density 7.rootmeansquare 8.trade off 9.lower bound 1.equalizer 11.vice versa 12.upper
10、limit Exercises物理系统,实际系统物理系统,实际系统上升时间上升时间信息量信息量理论上,标准上理论上,标准上高斯信道高斯信道概率密度概率密度均方根值均方根值,均方根;均方根均方根;均方根()交替换位,折衷选择交替换位,折衷选择下界下界,下限下限均衡器均衡器反之亦然反之亦然上限上限第7页.Please translate the following words and phrases into English.1.通信理论2.香农定理3.信道带宽4.信号波形5.理想低通滤波器 6.自相关函数7.无噪声高斯信道 8.通信信道9.信息速率10.信噪比Exercisescommunica
11、tion theory(theory of communications)Shannons theoremchannel bandwidthsignal waveformideal lowpass filterautocorrelation functionnoiseless gaussian channelcommunication channelinformation rateSignal to noise ratio(SNR,S/N)第8页Exercises11.信道容量12.双边功率谱密度13.误码率14.奈奎斯特采样速率15.限带高斯信道16.高斯白噪声channel capacit
12、yTwo sided power spectral densityerror probability(probability of error)Nyquist sampling rateband limited gaussian channelwhite Gaussian noise第9页Exercises.Fill in the blanks with the missing word(s).1.There is a negative statement associated Shannons theorem.2.the purpose of transmission over the ch
13、annel,the messages are represented by fixed voltage levels.3.Since the transmission of any of the M messages is equally likely,H=log2M,thus our channel is transferring information a rate R=rH.4.For a fixed signal power and the presence of white gaussian noise the channel capacity approaches an upper
14、 limit with increasing bandwidth.5.It is great interest to recognize that the tradeoff between bandwidth and signal to noise ratio is not limited by a lower limit bandwidth.withonatinofin第10页Exercises6.The signal is transmitted a channel which can be represented as a lowpass RC circuit with cutoff a
15、t 1 Hz.7.If there is no noise,then we are entirely free to make for the attenuation by the use of an amplifier and to correct the frequency distortion by the use of an equalizer.8.That is,we need to estimate the interval T which should be assigned to each message to allow the transmitted levels to b
16、e recognized Individually the receiver,even though the bandwidth B of the channel is limited.9.Therefore,the 25 percent reduction bandwidth requires a 60 percent increase signal power.inasinofover第11页Exercises10.While we have used the term communication channel many occasions,it is well to emphasize
17、 at this point,that the term,which is Something an abstraction,is intended to encompass all the features and componentparts of the transmission system which introduce noise or limit the bandwidth.11.The probability of error is close unity for every possible set of M transmitter signals.12.It turns o
18、ut the results obtained for a gaussian channel often provide a lower bound the performance of a system Operating a nongaussian channel.inthatintoinas第12页.Please translate the following words and phrases into Chinese.1.overall performance 2.crest factor 3.nonlinear operation 4.inverse operation5.rms
19、6.PAM 7.PDM 8.PPM 9.maximum magnitude 10.error intervals11.Entropy12.round off13.quantum level 14.DPCMExercises总性能总性能振幅振幅(波峰波峰)因数因数(振幅与有效值之比振幅与有效值之比)非线性运算非线性运算逆操作逆操作均方根均方根(值值)脉幅调制脉幅调制(pulse amplitude modulation)脉宽调制脉宽调制(pulse duration modulation)脉脉(冲相冲相)位调制位调制(pulse phase modulation)最大幅值最大幅值误差间隔误差间隔
20、熵熵,平均信息量平均信息量舍入,用四舍五入化为整数舍入,用四舍五入化为整数量化电平量化电平差分脉冲编码调制差分脉冲编码调制(differential pulse code modulation)第13页Exercises.Please translate the following words and phrases into English.1.正脉冲2.脉冲编码调制3.解码器4.编码器5.量化步长6.峰值7.线性函数8.脉冲序列9.均匀量化器10.预测编码11.压扩器12.压缩比 positive pulsepulse code modulation(PCM)decoderencoderq
21、uantum step sizepeak magnitudeslinear functionpulse trainuniform quantizerpredictive codingCompandorcompression ratio第14页Exercises.Fill in the blanks with the missing word(s).1.PCM is a widely different form of modulation compared with the analog pulse types such PAM,PDM,and PPM.2.The characteristic
22、s of the pulse group are related the message sample through operations called quantization and coding.3.The term symbol coder distingnishes this coding operation the overall source encoding process.In most cases,a variablelength code is used to represent the mapped and quantized data set.It assigns
23、the shortest codewords the most frequently (occurring,occure,occurred)output values and thus reduces coding redundancy.4.Thus,a quantization error exists PCM and,as will be seen,is the Basic limitation in performance.5.Quantization and sampling produce the same result sampling and quantizing.astofro
24、mtooccuringinas第15页Exercises6.For equal peak magnitudes,signals with large crest factors give poorer performance those with small Kcr.7.In the receiver the inverse operation is implemented an expandor restore the original message.8.The digital data is fed serially the decoder.9.the rate drops,sample
25、s are made less frequently and step sizes increase.10.The actual compression ratio resulting this method is no more than an order of 41.11.In an attempt to (reduce,reducing)the number of codes sent by a PCM system,a slight variance sampling method is used by a system known Differential Pulse Code Mo
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