【正文】 hip between the nature of system and the periodicity of its frequency response: a continuous 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)有非周期性的頻率響應，而離散系統(tǒng)有周期性的頻率響應。2. Linear filters amplify or attenuate selected spatial frequencies, can achieve such effects as smoothing and sharpening, and usually form the basis of resampling 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)像平滑和銳化這些效果，通常是重采樣和邊緣檢測算法的基礎。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 varies.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。注意，在本書中粒子運動僅限于金屬的情況不屬于電子學。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 dialogue 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?？萍加⒄Z課件 ExercisesUnit 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。 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 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。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起著重要作用，而軟件及數(shù)字處理方面卻沒能與硬件同步發(fā)展。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 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。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擇代表信號的字長而獲得。5. The main function of the receiver is to extract the input message signal from the degraded version of the transmitted signal ing 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。2. Computations show a reduction of 6dB in the EM field intensity with the distance 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。3. Like transfer of heat by conduction, convection and radiation, microwave heating can be considered 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(chǎn)生于發(fā)生介電損耗的地方。5. Other motivations for using CAD in circuit design includes the wish to acquire confidence in a design that was acplished by other means, and, not least in importance, a sense 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。（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 these amplifiers pensates 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。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 exchange 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。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)。經(jīng)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。不過通信也可以用光波頻段上的電磁載波來實現(xiàn)。一個電子通信系統(tǒng)包括：支持信息流動所需要的設備，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，以及對所有這些資源的管理。3. First generation munications 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). They suffered from a low user capacity, and security problems due to the simple radio interface used. Second generation systems were introduced in the early 1990’s, and all use digital technology. This provided an increase in the user capacity of around three times, achieved by pressing the voice waveforms before transmission. Third generation systems are an extension on the plexity of secondgeneration 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 plex multiplex access techniques 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。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。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。4. For each bination of munication (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 readily 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 handhel