搜索
1.Thiselectronbeamsweepsacrosseachlineatauniformrate，thenfliesbacktoscananotherlinedirectlybelowthepreviousoneandsoon，untilthehorizontallinesintowhichitisdesiredtobreakorsplitthepicturehavebeenscannedinthedesiredsequence．电子束以均匀的速率扫描每一行，然后飞速返回去扫描下一行，直到把被扫描的图像按所希望的顺序分割成行。2.Thetechnicalpossibilitiescouldwellexist，therefore，ofnation-wideintegratedtransmissionnetworkofhighcapacity，controlledbycomputers，interconnectedgloballybysatelliteandsubmarinecable，providingspeedyandreliablecommunicationsthroughouttheword因此，在技术上完全可能实现全国性的集成发送网络。这种网络容量大，由计算机控制，并能通过卫星和海底电缆实现全球互联，提供世界范围的高速、可靠的通信。3.Transittimeistheprimaryfactorwhichlimitstheabilityofatransistortooperateathighfrequency．渡越时间是限制晶体管高频工作能力的主要因素4.Theintensityofsoundisinverselyproportionaltothesquareofthedistancemeasuredfromthesourceofthesound.声强与到声源的距离的平方成反比。5.Theattenuationofthefilterisnearlyconstanttowithin0.5dBovertheentirefrequencyband．该滤波器的衰减近于恒定,整个频带内的变化在0.5dB以内。6.Atpresent,thestateofmostsemiconductordevicetechnologyissuchthatthedevicedesignandprocesstechnologymustbesupplementedbyscreeningandinspectionprocedures,ifultimatedevicereliabilityistobeobtainedandcontrolled．目前,大多数半导体器件的技术尚未十分完善,以至若要获得并控制器件最终的可靠性,就必须辅以筛选和检验,以弥补设计和工艺技术之不足7.Bandwidthoftransistoramplifiersvaryfromabout250MHzintheLbandto1000MHzintheXband．晶体管放大器的带宽在L波段约为250MHz,在X波段为1000MHz。8.Theoutputofthedifferentialamplifierisfedtothecircuit’soutputstageviaanoffset-compensationnetwork,whichcausestheop-amp’soutputtocenteratzerovolts.Theoutputstagetakestheformofacomplementaryemitterfollower,andprovidesalow-impedanceoutput.差动放大级的输出通过一个失调补偿网络与输出级相连,目的是使运放的输出以0V为中心。输出级采用互补的射极跟随器的形式以使输出阻抗很低9.Becauseoftheveryhighopen-loopvoltagegainoftheop-amp,theoutputisdrivenintopositivesaturation(closeto+V)whenthesamplevoltagegoesslightlyabovethereferencevoltage,anddrivenintonegativesaturation(closeto-V)whenthesamplevoltagegoesslightlybelowthereferencevoltage.由于运放的开环电压增益很高,当取样电压略高于参考电压时,输出趋向于正向饱和状态(接近+V)。当取样电压低于参考电压时,输出趋向于负向饱和状态(接近-V)。10.Ifthesignalsourceweredirectconnectedinsteadofcapacitorcoupled,therewouldbealowresistancepathfromthebasetothenegativesupplyline,andthiswouldaffectthecircuitbiasconditions.如果信号源和电路不是用电容耦合而是直接相连，从基极到负电源线就会一个低阻通路，并且这将影响到电路偏置状态11.Thedifferentialamplifierhasahigh-impedance(constant-current)“tail”togiveitahighinputimpedanceandahighdegreeofcommon-modesignalrejection.Italsohasahigh-impedancecollector(ordrain)load,togiveitalargeamountofsignal-voltagegain(typicallyabout100dB).差动放大极有一个高阻抗的“尾巴”（恒流源）以提供高输入阻抗和对共模信号的深度抑制，同时，它还具有一个高阻抗和集电极或漏极负载以提供高的信号电压增益（典型的数据是100dB).12.Ontheotherhand,aDCnegative-logicsystem,asinFigure3.6(b),isonewhichdesignatesthemorenegativevoltagestateofthebitasthe1levelandthemorepositiveasthe0level.另一方面,如图3.6(b)所示,把比特的较低的电压状态记为1电平,较高的电压状态记为0电平,这样的系统称13.Forexample,torepresentthe10numerals(0,1,2,…,9)andthe26lettersoftheEnglishalphabetwouldrequire36differentcombinationsof1’sand0’s.Since253626,thenaminimumof6bitsperbitearerequiredinordertoaccommodateallthealphanumericcharacters.例如，要表示0～9十个数字和英文字母表中的26个字母，就需要0和1的36种不同的组合。因为253626,所以,为了能表示所有的字母和数字，要求每个字节最少要6个比特。14.A1signifiestheexistenceofapositivepulseinadynamicpositive-logicsystem;anegativepulsedenotesa1inadynamicnegative-logicsystem;a0ataparticularinput(oroutput)atagiveninstantoftimedesignatesthatnopulseispresentatthatparticularmoment.在动态正逻辑系统中，1表示有一个正脉冲存在，而在负逻辑系统中，负脉冲表示为1。不管那种系统，某一时刻在某一输入端（或输出端）的0，均表示此刻无脉冲。15.Intergradedcircuitsarealsoclassifiedaccordingtotheirfunctions.DigitalorlogicalICareusedasswitches,theyareeitheronoroff.Incomputerstheonandoffstatescorrespondto0or1.OtherICiscalledlinearoranalogIC.也可根据其功能不同对集成电路进行分类。数字IC(也称为逻辑IC)通常用作开关,表示接通或关断。在计算机中,接通和关断状态分别对应“0”或“1”。另一种IC被称为线性或模拟IC。16.Thereductioninpowerdissipationisparticularlyimportantwhereacomplexcircuitistobeconcentratedintoasmallspace.Theproblemofextractingtheheatgeneratedinthecircuitmaythenbeadifficultone.减小功率损耗是非常重要的,其方法是将一个复杂的电子线路集成为一小块。这使得释放电路工作时产生的热量变成一个难题。17.BothN-typeandP-typesemiconductorsaremadebytreatedmaterials,suchasgermaniumandsiliconwithimpuritiessuchasarsenicandindium.N型半导体和P型半导体是利用杂质掺入纯净半导体而形成的,如将杂质砷和铟掺入锗和硅中18.Inaddition,thesignalprocessormayalsoaddparitybitstothedigitalwordtoprovidechannelcodingsothaterrordetectionandcorrectioncanbeusedbythesignalprocessorinthereceivertoreduceoreliminatebiterrorsthatarecausedbynoiseinthechannel.此外,信号处理器还可以给数码字加入奇偶校验位,即提供信道编码,使得接收机的信号处理器可以进行误码检测和纠错,以减少或消除由信道噪声所引起的误码。19.Furthermore,weshallprovethataminimumtheoreticalsamplingfrequencyoforder6.8kilohertz(kHz)isrequiredtoconveyavoicechanneloccupyingtherange300Hzto3.4kHz.而且我们将证明,为了变换频率范围为300Hz~3.4kHz的话路信号,理论上的最小采样频率为6.8kHz。20.Bycomparison,mostotherformsoftransmissionsystemsconveythemessageinformationusingtheshape,orlevelofthetransmittedsignal;parametersthataremosteasilyaffectedbythenoiseandattenuationintroducedbythetransmissionpath.相比之下,许多其他形式的传输系统是利用被传信号的波形或电平的高低来传送信息的,而这些参数又极易受到传输路径中的噪声和衰耗的影响。21.Dependingontherelationshipbetweenthesignalfrequenciesandthesamplingrate,spectralinversionmaycausetheshapeofthespectruminthebasebandtobeinvertedfromthetruespectrumofthesignal.根据信号频率和采样频率之间的关