信息科學與電子工程專業(yè)英語課后答案

1、Unit 1 Exercises(1) Translate the following sentences into Chinese.1. As with series resonance, the greater the resistance in the circuit the lower the Q and, accordingly, the flatter and broader the resonance curve of either line current or circuit impedance.對于串聯(lián)諧振，電路中的電阻愈大Q值就愈低，相應地線路電流或電路阻抗的諧振曲線也就

2、愈平、愈寬。2. A wire carrying a current looks exactly the same and weighs exactly the same as it does when it is not carrying a current.一根帶電的導線其外表與重量都與不帶電導線完全一樣。3. Click mouse on the waveform and drag it to change the pulse repetition rate, or directly enter a new value of the period in the provided dial

3、ogue box, while keeping the pulse width unchanged.在波形上點擊鼠標并拖動來改變脈沖重復頻率，或者在提供的對話框中直接輸入新的周期值，而保持脈沖寬度不變。4. Electronics is the science and the technology of the passage of charged particles in a gas, in a vacuum, or in a semiconductor. Please note that particle motion confined within a metal only is not

4、 considered electronics.電子學是一門有關帶電粒子在氣體、真空或半導體中運動的科學技術。注意，在本書中粒子運動僅限于金屬的情況不屬于電子學。5. Hardware technologies have played vital roles in our ability to use electronic properties to process information, but software and data processing aspects have not developed at the same speed.硬件技術在我們使用電子特性來處理信息的能力中一直

5、起著重要作用，而軟件與數(shù)字處理方面卻沒能與硬件同步發(fā)展。6. However, in a properly designed DC amplifier the effect of transistor parameter variation, other than Ico, may be practically eliminated if the operation point of each stage is adjusted so that it remains in the linear operation range of the transistor as temperature v

6、aries.然而在設計得當?shù)闹绷鞣糯笃髦?，若調節(jié)每一級的工作點使之在溫度變化時保持在晶體管線性區(qū)，就能在實際上消除Ico以外的晶體管參數(shù)變化所造成的影響。Unit 2 Exercises (1) Translate the following sentences into Chinese.1. If analog signals are to be transmitted digitally, they first have to be sampled at a specified rate and further converted to discrete amplitude samples

7、 by quantization.如果要以數(shù)字方式傳輸模擬信號，首先必須以一定的頻率對信號進行采樣，然后通過量化進一步將它們轉換為離散的幅度樣本。2. Linear filters amplify or attenuate selected spatial frequencies, can achieve such effects as smoothing and sharpening, and usually form the basis of re-sampling and boundary detection algorithms. 線性濾波器放大或衰減選擇的空間頻率，能夠實現(xiàn)像平滑和銳

8、化這些效果，通常是重采樣和邊緣檢測算法的基礎。3. Stability and repeatability are fundamental attributes of digital circuits, however, and the necessary accuracy can be obtained in a digital version of the modulator by an appropriate choice of word length to represent the signals.不過穩(wěn)定性和可重復性是數(shù)字電路的基本性質，在數(shù)字式調制器中必要的精度可通過適當?shù)剡x擇代

9、表信號的字長而獲得。4. The first observation is made on the fundamental relationship between the nature of system and the periodicity of its frequency response: acontinuous system has an aperiodic frequency response, while a discrete system has a periodic frequency response.從系統(tǒng)性質和它頻率響應的周期性之間的基本關系中首先可以看到：連續(xù)系統(tǒng)有

10、非周期性的頻率響應，而離散系統(tǒng)有周期性的頻率響應。5. The main function of the receiver is to extract the input message signal from the degraded version of the transmitted signal coming from the channel.接收器的主要功能是從由信道傳輸來的退化了的信號中提取出輸入消息。Unit 3 Exercises(1) Translate the following sentences into Chinese.1. A very commonly used

11、method of microwave measurements is based on the study of a standing wave pattern formed along the line because of the interference of incident and reflected waves.一個很常用的微波測量方法是基于對駐波圖型的研究，這種駐波是由入射波和反射波之間的干涉而沿著傳輸線形成的。2. Computations show a reduction of 6dB in the EM field intensity with the distance

12、doubled, and an increase of 3dB in the intensity with the transmitted power doubled. This result provides verification to the algorithm used.計算表明，當距離增大一倍時，電磁場強度減小6分貝；而發(fā)射功率增大一倍時，場強則增加3分貝。這一結果驗證了所用算法的正確性。3. Like transfer of heat by conduction, convection and radiation, microwave heating can be conside

13、red as another mode of heat transfer, in which heat is produced directly at the location of the dielectric losses.就像通過傳導、對流、輻射來傳遞熱量一樣，微波加熱可以看作熱傳遞的另一種方式，即熱量直接產生于發(fā)生介電損耗的地方。4. Operation of the radar is based on the measurement of the time it takes for a pulse transmitted from an antenna to get reflecte

14、d by the object to be detected and to return at the antenna and the receiver.雷達的工作是基于對天線發(fā)出的脈沖被所要探測的目標反射，（然后）回到天線和接收機所需時間的測量。5. Other motivations for using CAD in circuit design includes the wish to acquire confidence in a design that was accomplished by other means, and, not least in importance, a s

15、ense of curiosity or perhaps a desire to discover the unexpected.在電路設計中使用CAD的其它動機包括：想要驗證用別的方法設計出來的電路；滿足好奇心或者可能是想發(fā)現(xiàn)預想不到的現(xiàn)象。后一個動機并非是最不重要的。（取得信心，并非最不重要，意料之外的事）6. The spacing between the repeating amplifiers is a function of the cable attenuation and the system bandwidth so that the gain provided by the

16、se amplifiers compensates for the loss introduced by the cable.中繼放大器之間的間距是電纜衰減和系統(tǒng)帶寬的函數(shù)，以便這些放大器提供的增益補償電纜引起的損耗。7. When the cut-off frequency is no less than the maximal frequency of the original signal,nor isit greater than the differencebetweenthe sampling frequency and the maximal frequency, the ori

17、ginal signal may be completely rebuilt.當截止頻率不小于原始信號的最高頻率，也不大于采樣頻率和最高頻率之差，原始信號可以完整地重建。8. While the politics of the last one hundred years centered around Industrial Age technology, the politics of the future will be based on Information Age concerns oriented towards the storage, protection and exchan

18、ge of information.盡管近百年來的政治活動是以工業(yè)時代的技術為中心的，未來的政治活動將基于信息時代的事物，面向信息的存儲、保護和交換。Unit 4 Exercises (1) Translate the following passages into Chinese.1. Communication may be broadly defined as the transfer of information from one point to another. When the information is to be conveyed over any distance a c

19、ommunication system is usually required. Within a communication system the information transfer is frequently achieved by superimposing or modulating the information on to an electromagnetic wave which acts as a carrier for the information signal. This modulated carrier is then transmitted to the re

20、quired destination where it is received and the original information signal is obtained by demodulation. Sophisticated techniques have been developed for this process by using electromagnetic carrier waves operating at radio frequencies as well as microwave and millimeter wave frequencies. However,

21、communication may also be achieved by using an electromagnetic carrier that is selected from the optical range of frequencies.通信可以廣義地定義為從一處到另一處的信息傳遞。當要將信息傳輸?shù)饺魏尉嚯x以外時就需要有一個通信系統(tǒng)。在通信系統(tǒng)部，信息的傳輸經常通過將信息疊加或調制到作為信號載體的電磁波上來實現(xiàn)。經調制的載波然后被傳送到要求的目的地，在那里被接收，原始信號通過解調被恢復出來。為了實現(xiàn)這一過程，已經利用工作在射頻、微波以與毫米波頻率上的電磁載波開發(fā)了復雜的技術。不過

22、通信也可以用光波頻段上的電磁載波來實現(xiàn)。2. Electronic communications is the transfer and movement of data between locations through the use of computers. An electronic communication system includes the equipment needed to support the movement of information, the communication lines and media to carry the information, t

23、he computer software and programs to control the flow of information, the personnel to plan, implement, and operate communications, and the management of all these resources. Electronic communications establishes links between people as well as computers.電子通信就是通過使用計算機在不同的地點之間傳輸數(shù)據(jù)。一個電子通信系統(tǒng)包括：支持信息流動所需

24、要的設備，承載信息的通信線路和媒介，控制信息流的計算機軟件和程序，計劃、實施、操作通信系統(tǒng)的人員，以與對所有這些資源的管理。電子通信建立起人和人、計算機和計算機之間的聯(lián)系。3. First generation communications systems can be characterized by the use of analog transmission techniques, and the use of simple multiplex access techniques such as frequency division multiple access (FDMA). The

25、y suffered from a low user capacity, and security problems due to the simple radio interface used. Second generation systems were introduced in the early 1990s, and all use digital technology. This provided an increase in the user capacity of around three times, achieved by compressing the voice wav

26、eforms before transmission. Third generation systems are an extension on the complexity of second-generation systems and are to be introduced after the year 2000. The system capacity will be increased to over ten times original first generation systems, achieved by using complex multiplex access tec

27、hniques such as code division multiplex access (CDMA), or an extension of TDMA, and by improving flexibility of services available.第一代通信系統(tǒng)以模擬傳輸技術和簡單復用技術如頻分復用為特征。這些系統(tǒng)用戶容量低，而且因為使用簡單的無線電接口而存在安全問題。第二代通信系統(tǒng)于20世紀90年代初開始引入，全部使用數(shù)字技術。通過在傳輸前將話音波形壓縮使得用戶容量提高了三倍。第三代通信系統(tǒng)是對第二代系統(tǒng)在復雜性方面的擴展，預計于2000年以后啟用。通過使用復雜的復用技術如CD

28、MA或TDMA的擴展，并提高服務的靈活性使得系統(tǒng)容量比原來的第一代系統(tǒng)提高10倍。4. For each combination of communication (modulation/detection) type, channel fading model, and diversity type, the average bit error rate (BER) and/or symbol error rate (SER) of the system is obtained and represented by an expression in a form that can readi

29、ly be evaluated. All cases considered correspond to real practical channels, and in many instances the BER and SER expressions obtained can be evaluated numerically on a hand-held calculator.對于通信（調制/檢測）類型、信道衰落模型、分集類型的每一種組合，得到系統(tǒng)的平均誤碼率（BER）和符號錯誤率（SER），并以容易求值的形式表示。所有考慮的相應于實際信道的情況，以與許多情況下得到的BER和SER表達式均可

30、用手持計算器來計算。5. Modulation is the systematic variation of some attribute of a carrier waveform such as the amplitude, phase, or frequency in accordance with a function of the message signal. It is used in communication systems for matching signal characteristics to channel characteristics, for reducing

31、 noise and interference, for simultaneously transmitting several signals over a single channel, and for overcoming some equipment limitations. A considerable portion of this book is devoted to the study of how modulation schemes are deigned to achieve the above tasks. The success of a communication

32、system depends to a large extent on the modulation.調制是載波波形的某些屬性，例如幅度、相位和頻率，根據(jù)消息信號的函數(shù)有規(guī)則的變化。它用于通信系統(tǒng)以使信號特性匹配信道特性，減少噪聲和干擾，在單個信道上同時傳輸多個信號，并克服某些設備的限制。本書相當大部分容是研究如何設計調制方案以實現(xiàn)上述任務。一個通信系統(tǒng)的成功很大程度上依賴于調制。Unit 5 Exercises (1) Translate the following passage into Chinese.OFDM consists of a large number of subcarr

33、iers equally spaced in a frequency band, each may be digitally modulated by a same scheme such as PSK, QAM, etc., or by different schemes. A serially transmitted sequence is divided into a number of sections, each having N symbols, and the N symbols in each section are used to modulate N carriers fo

34、r simultaneous transmission. Therefore OFDM is essentially a parallel modulation system. When the number of subcarriers is sufficiently large, the system can resist multipath interference. This is because that, in the time domain, a symbol duration longer than the multipath delay can be chosen, whil

35、e in the frequency domain, each symbol only occupies a small portion of the channels frequency band. Thus, the effect of multipath fading spreads over many symbols, resulting in slight distortion to many symbols rather than complete destroy of a few symbols. In this way, correct demodulation is not

36、affected so that the signal can be accurately recovered at the receiver. In an OFDM system, the principle of choosing the subcarrier interval is to make the subcarriers mutually orthogonal within the entire symbol period. Thus, even if spectral overlap exists between the subcarriers, the symbols can

37、 still be recovered without loss. In order to realize maximum spectral efficiency, the interval between subcarriers is usually chosen to equal the reciprocal of the symbol duration T. Therefore the subcarrier frequencies in the base band are fn = n/T, (n = 0, 1, . , N-1). Denoting the n-th modulatin

38、g symbol as X(n), the OFDM waveform within a symbol duration can be expressed as:(1)Sampling this waveform att = T/N yields(2)It is observed from the above expression that x(k) and X(n) form a discrete Fourier transform pair, therefore the baseband OFDM waveform can be generated from the discrete Fo

39、urier transform of N modulating symbols. When N=2m where m is an integer, the fast algorithm of IDFT is easy to implement.OFDM由大量在頻率上等間隔的子載波構成。每個子載波可用同樣的方案，如PSK，QAM等，或者用不同的方案數(shù)字調制。將串行傳輸?shù)姆栃蛄蟹殖稍S多段，每一段有N個符號，每段的N個符號被用來分別調制N個載波同時發(fā)送。因此，OFDM本質上是一個并行調制系統(tǒng)，當載波數(shù)足夠大時，這種系統(tǒng)具有抗多徑干擾的能力。這是因為在時域上符號周期能選取得比多徑延遲時間長，而在頻域

40、上每個符號只占整個信道帶寬的一小部分，因此多徑衰落的影響被分散到許多符號上，其結果是許多符號都發(fā)生輕度的畸變，而不是使某些符號被完全破壞。這樣，不影響正確的解調，信號能在接收器中準確地恢復。在OFDM系統(tǒng)中，選擇子載波間隔的原則是使子載波在整個符號周期相互正交，這樣。即使在子載波間存在頻譜部分重疊，符號仍能無損失地恢復。為了實現(xiàn)最大的頻譜效率，子載波之間的間隔通常選取為符號周期的倒數(shù)。因此基帶子載波頻率為fn = n/T, (n = 0, 1, . , N-1)，第n個調制符號記為X(n)，在一個符號周期的OFDM波形可表示：(1)在t = T/N時刻采樣這個波形得到：(2)從上面的表示中可以

41、看到，x(k) 和X(n)構成了一對離散傅里葉變換，因此基帶OFDM波形可根據(jù)N個調制符號的離散傅里葉變換來生成。當N=2m，其中m為整數(shù)，IDFT的快速算法很容易實現(xiàn)。Unit 6 Exercises (1) Translate the following sentences into Chinese.1. Communication is the transmission of information from one point to another. This transmission requires the ability to vary signals with time in

42、a manner which is unpredictable to the receiver.通信就是信息從一點傳送到另一點。這種傳送要求信號隨時間發(fā)生的變化不能在接收端預測。2. It is true of any communication system that the shape and amplitude of the transmitted signal will be continuously degraded by the introduction of noise, and the attenuation along the transmission path.傳輸?shù)男盘枙?/p>

43、不斷地被噪聲的引入和線路上的衰減所損傷，對任何通信系統(tǒng)都是如此。3. Since the very beginning, communications systems have consisted of three major parts, namely, the equipment, the medium, and the protocol. It is still the case today. However, the close link of telecommunications with the computer technology has brought about treme

44、ndous changes in communications, from the concepts, to the contents and the methods.從一開始通信系統(tǒng)就由設備、媒介和協(xié)議三個要素組成。至今依然如此。然而電信與計算機技術的緊密聯(lián)系使得通信從概念到容和手段都發(fā)生了重大的變化。4. The availability of such a large collection of system performance curves in a single compilation allows the researcher or system designer to per

45、form trade-off studies among the various communication type/fading channel/diversity combinations so as to determine the optimum choice in the face of his or her available constraints.在一本書中提供如此大量的系統(tǒng)性能曲線，使研究者或系統(tǒng)設計者能在各種通信類型、衰落信道、分集組合之間進行比較研究，從而在他或她所面臨的限制之下做出最佳的選擇。5. The channel provides the electrical

46、 connection between the information source and the user. The channel can have many different forms such as a microwave radio link over free space, a pair of wires, or an optical fiber.信道提供信息源和用戶之間的電路聯(lián)接。信道可以有許多不同的形式，比如自由空間里的微波聯(lián)接，一對電線，或者一根光纖。6. The degradation of the transmitted signal is a result of

47、signal distortion due to imperfect response of the channel and due to undesirable electrical signals (noise) and interference. Noise and signal distortion are two basic problems of electrical communication.傳輸信號的退化是信號失真的結果，而這種失真又是由信道的非理想響應與不想要的電信號（噪聲）和干擾引起的。噪聲和信號畸變是電子通信的兩個基本問題。Unit 8 Exercises (1) Tr

48、anslate the following sentences into Chinese.1. Early in the twentieth century, it was found that light could cause atoms to emit electrons and that, when light released an electron from an atom, the energy possessed by the electron very greatly exceeded that which the atom could, according to the e

49、lectromagnetic wave theory, have received.在二十世紀早期，人們發(fā)現(xiàn)光能夠使原子放出電子，而且當光從原子中釋放一個電子時，電子所包含的能量大大超過由電磁波理論得到的原子所接收的能量。2. Pulse broadening determines the minimum separation between adjacent pulses, which in turn determines the maximum information-carrying capacity of the optical fiber.脈沖的展寬決定了相鄰脈沖之間的最小間隔，這一

50、間隔進而又決定了光纖的最大信息容量。3. If one were to transmit such information without impressing it on an optical carrier but instead on a radio frequency (RF) carrier a bit higher than the maximum rate, the transmission wavelength of the RF carrier would be centimeters or larger.如果傳輸這樣的信息不是將它加載到光纖上，而是加載在略高于最大速率的射頻

51、載波上，則此射頻載波就會是厘米波或是波長更長一些的波。4. Thesmallness of the optical wavelength, therefore, allows for the miniaturization of transmit and receive modules, which should allow considerable reduction in size, weight, and cost of optical communication systems with respect to microwave/radio wave counterparts.光波波長

52、之小使發(fā)射和接收模塊得以小型化，這就使光通信系統(tǒng)的尺寸、重量以至價格與相應的微波、無線電波通信系統(tǒng)相比都大為降低。5. Although all the advantages of coherent optical communication systems have yet to be brought to fruition, another property of optical radiation has made todays optical communication systems not desirable for applications.雖然相干光通信系統(tǒng)的所有優(yōu)點還有待于落

53、實在具體成果中，光輻射的另一性質卻使目前的光通信系統(tǒng)不利于應用。6. When coupled with lights short wavelength which allows for miniature sources and detectors and micron-sized waveguides, direct detection schemes have allowed for small, lightweight, high bandwidth systems which are competitive in many areas, most notably to the pre

54、sent telecommunications transmission, although a myriad of other applications are continually opening up.光的波長很小，可以使用小型的光源和檢測器以與微米級的波導，于是用直接檢測方案可實現(xiàn)在許多領域具有競爭力的小巧的寬帶系統(tǒng)，這些領域中特別引人注目的是當前電信傳輸中的應用，盡管無數(shù)其他應用也在不斷涌現(xiàn)出來。7. As mentioned previously, these applications have tended to open up more slowly than origina

55、lly predicted, as cost was really not much of a consideration in telecommunications, where equipment costs are swamped by other considerations.如前所述，（線路）成本并非電信系統(tǒng)中真正重要的考慮因素，通信設備的成本主要受到其他因素的制約，因此這些應用比預料的出現(xiàn)得慢。8. As wavelengths decrease to approach the size of circuit components, circuit elements are no

56、longer lumped as such, and leads can act as reflective components and/or antennas and lumped elements as electromagnetic resonators.隨著波長減小到接近于電路元件的尺寸，電路單元就不再是集總的，導線可起到反射元件以與（或）天線的作用，集總單元則成為電磁諧振器。UNIT 101.The principles which underlie almost all digital audio applications and devices, be they digital

57、 synthesis, sampling, digital recording or CD or iPod playback, are based on the basic concepts which follow in this chapter. New forms of playback, file formats, compression and storage of data are all changing on a seemingly daily basis, but the underlying mechanisms for converting real-world soun

58、d into digital values, manipulating those data and finally converting them back into real-world sound has not varied much since Max Mathews developed MUSIC I in 1957 at Bell Labs.所有的數(shù)字音頻應用程序和設備是在數(shù)字合成、采樣、數(shù)字錄音或CD或iPod播放的基礎上，都是基于最基本的概念,遵循在這一章的原則。新形式的播放,文件格式,壓縮和存儲的數(shù)據(jù)都在一個看似每天改變，但是這種聯(lián)系的潛在機制轉換為現(xiàn)實世界的聲音轉化為數(shù)字

59、值,操縱這些數(shù)據(jù),最后將他們轉化成真實世界的聲音沒有變化多少，因為馬克斯馬修斯在貝爾實驗室于開發(fā)了音樂于20世紀60年代。2.Sound is created by vibrations, such as those produced by a guitar string, vocal cords or a speaker cone. These vibrations move the air molecules near them, forcing molecules together, as a result raising the air pressure slightly. The air molecules that are under pressur