1、在波形上点击鼠标并拖动来改变脉冲重复频率,或者在提供的对话框中直接输入新的周期值,而保持脉冲宽度不变。 4.Eectroncs is the science and the techology oftepas ofchrgd pricesin a gas,i avacuum,or i a semioducor.ls ntthat pariclmotioncofine wtin ametl only is notcnsideredeectroics电子学是一门有关带电粒子在气体、真空或半导体中运动的科学技术。注意,在本书中粒子运动仅限于金属的情况不属于电子学。5.Hardwr tcholosae
2、 pyed vitrles in our aility o eectroc roperiesto rocess information, b softwareand dat pocesing aspecs ave ot veloedat the same spee.硬件技术在我们使用电子特性来处理信息的能力中一直起着重要作用,而软件及数字处理方面却没能与硬件同步发展。6.Howevr, in proerly designed DC amplfier the effet of raiso aameter varation, h tha Ico, may be ratically elimnat
3、ifth opeaton poin eahstage iadjs sothat iremains in theinear opertion rae fhe trasistor a empertur vares.然而在设计得当的直流放大器中,若调节每一级的工作点使之在温度变化时保持在晶体管线性区,就能在实际上消除Ico以外的晶体管参数变化所造成的影响。nit 2 xeriss (1) Tansate thfolongsntncesinto hinese1. analo ilare t be trnsmited dgilly, they firthato bampled a specified r
4、at anfurthrconerte to dscr aplitud smlesby qantizatin.如果要以数字方式传输模拟信号,首先必须以一定的频率对信号进行采样,然后通过量化进一步将它们转换为离散的幅度样本。2.Linear fiters ampliy or ateuaeselece spail frequenies,can achiv sh efes assotng nd shpeng, anuly f th basis ofresamlng andboudar detection algrihms. 线性滤波器放大或衰减选择的空间频率,能够实现像平滑和锐化这些效果,通常是重采样
5、和边缘检测算法的基础。3.taiityan reptabilityare fundaetlattribtes of igial crcs, howeer, andth neesayacuracy ca b btaind ina digital vsion f the ouator byan pppriate coice oordlength t rpresthe gl不过稳定性和可重复性是数字电路的基本性质,在数字式调制器中必要的精度可通过适当地选择代表信号的字长而获得。4.The firtoervation made on he undmental laionshi betwnthe nat
6、u of sstemnd the periocy f s fequecy repne: oninuou system h aaeriodic frequenc repne,hile dsretsytm as periodic freqey esose.从系统性质和它频率响应的周期性之间的基本关系中首先可以看到:连续系统有非周期性的频率响应,而离散系统有周期性的频率响应。5.Than funct f the cirisoetract te inpu messag sgnal from th dgrdd verio ofthetranmttesignal comg o can.接收器的主要功能是从
7、由信道传输来的退化了的信号中提取出输入消息。 Uit3 eise() Translte th followin sentnestohine1.A ver oony ed method of miroae easurmetssbas o thestudy ofa sning vepattrn frmd alog tlne ecus of e interferc of incidentnd refleced waes一个很常用的微波测量方法是基于对驻波图型的研究,这种驻波是由入射波和反射波之间的干涉而沿着传输线形成的。2.Cpttinhow arctioof 6 in the EM fieldin
8、enity it th distacebled,nd n increse 3dB in thintenity withth transmitt owr dobd Thisresul provies vriicaionto the algorthm use.计算表明,当距离增大一倍时,电磁场强度减小6分贝;而发射功率增大一倍时,场强则增加3分贝。这一结果验证了所用算法的正确性。3.Lke transfr f hat byonducin, covectionanradation, microwve hetn n conidered asanotermod of eat tansfe, inwhic
9、 hats roducddirel t the locat o te eletric losses 就像通过传导、对流、辐射来传递热量一样,微波加热可以看作热传递的另一种方式,即热量直接产生于发生介电损耗的地方。4.Opton o he ra is ased o heasuremetofthetim t a or apulse ransmitfom n atenna ogtreflete y te bject o e deecedand to reurnat th nena nd the receiver.雷达的工作是基于对天线发出的脉冲被所要探测的目标反射,(然后)回到天线和接收机所需时间的
10、测量。5.Othrmotivtionsfo unCAD in ircuit esgnlude the ih to acquir cndenc in design tat was ccomplishd yother mans, ad, no lest in mportace,asee of curiosiy r peraps a deire odiscovr the eeted.在电路设计中使用CAD的其它动机包括:想要验证用别的方法设计出来的电路;满足好奇心或者可能是想发现预想不到的现象。后一个动机并非是最不重要的。(取得信心,并非最不重要,意料之外的事)6.e angetweenth ree
11、tin amplifirs i a fnctonof the ble atenuatio an the sym banditho tha thegain prvide bythese aplifiersompensae for te lossintrdud b te cabe.中继放大器之间的间距是电缆衰减和系统带宽的函数,以便这些放大器提供的增益补偿电缆引起的损耗。7.Wh thecu-offfrquecy is o le thn te maxma frequency of the iginsial, r is greatha the ifrence etwethe mpling frequ
12、enc andemaxia frcy, he origial ignlmy becomlety rbit.当截止频率不小于原始信号的最高频率,也不大于采样频率和最高频率之差,原始信号可以完整地重建。8.Wile th pitcsof th lat ne undre yarenteraoundndustrial Age technolgy, thpiics f thefuureill bse on Informatn Agcocern orintedtwardstestoge, prtecon ndexchageo informai尽管近百年来的政治活动是以工业时代的技术为中心的,未来的政治活动
13、将基于信息时代的事物,面向信息的存储、保护和交换。Unt 4 eries (1) Translat the folwngpassages into Cinese.1.Communcation may be roadly defid a the trasferof ifomon from onepn tonothr. Whenenfrmton is t be conveyd overaydstanc comuicaionyte is usullyrered. With a comuicatio st the inormatio tasfer is freuentl chieed supeimpo
14、sing ormodulating theinon onto an elecoagntic wve hi acts as acarer for e ioration sinl. hsmdulated carreis transite tothereued tiatio wee ti ceived adtheoiginal infrmtiosigal is obtaie y dmdlatn. Sopisticated tchnques have ben dvloped for this process b usingeletronec arewaes opeating tradi frqueni
15、sas wel s mcrowve mlmer wav freqeies Hoevr,communiatio my o be achevedby usingan eleromgntic caier thats seectd fm teopicl ne of frequencis.通信可以广义地定义为从一处到另一处的信息传递。当要将信息传输到任何距离以外时就需要有一个通信系统。在通信系统内部,信息的传输经常通过将信息叠加或调制到作为信号载体的电磁波上来实现。经调制的载波然后被传送到要求的目的地,在那里被接收,原始信号通过解调被恢复出来。为了实现这一过程,已经利用工作在射频、微波以及毫米波频率上的
16、电磁载波开发了复杂的技术。不过通信也可以用光波频段上的电磁载波来实现。2.lectnc ommicaions is he trnsfe ndovet a ewen locations hrog the eof cmutrs. An lctri mmuniatonsyste inludes the equpment neded to supot th moement of inforation, the omnicato ns d meito cary the informaon, the cmputer stwe rogras tconrolthe flow f infrman, the pe
17、rsnnl to lan, impleet, anoprate commuiations, andt anagemnt of al ths reure.Elernccomnications etablisheinks etweeeopleasl scoters.电子通信就是通过使用计算机在不同的地点之间传输数据。一个电子通信系统包括:支持信息流动所需要的设备,承载信息的通信线路和媒介,控制信息流的计算机软件和程序,计划、实施、操作通信系统的人员,以及对所有这些资源的管理。电子通信建立起人和人、计算机和计算机之间的联系。3.Frst enrton comunicatios ssemscan b
18、chracerizd b the useof al tansmisionteciqe,and the se fiml ultlex cce techiqe suc sfrequency ivision utiple acess(MA) Thy uffered f a lo uer capci, nd curityprblemsdue to th simple adio interfce ud eond generain sstems er ntrodued n taly 190s, ad all use ditl tecnolog. This rvde an ireaei tuercapcit
19、y o arund three times, acievd comreigh voi waveformsefore rnsson Third enerati syms are an xteon onh complexty of second-geerati sytemsad are be introduce afthe year 2000 Te sysecapatywll b incased over tn tmes oriinl firt genaion sems, achied byusing cmexultiplexaccess technqe uch s code dvision ut
20、ip accs (CMA), or neeiofDMA, and by mroving libi osvices avable第一代通信系统以模拟传输技术和简单复用技术如频分复用为特征。这些系统用户容量低,而且因为使用简单的无线电接口而存在安全问题。第二代通信系统于2世纪9年代初开始引入,全部使用数字技术。通过在传输前将话音波形压缩使得用户容量提高了三倍。第三代通信系统是对第二代系统在复杂性方面的扩展,预计于00年以后启用。通过使用复杂的复用技术如CMA或A的扩展,并提高服务的灵活性使得系统容量比原来的第一代系统提高10倍。4.Foach cmiaton fommunicatin(mlatin
21、decion)ype, chnel fdinmodel, an dversitytpe,the average iterr at (BE) ad/or smbol erorate (S) f the systmobtaind ad rpsn by expresio ina fm tacareadi be evalated.l caesosidered coreson to rl practical chnnels, nd in many stanc th BER adEexpssons btinecanbe evalated nmericalyon a had-held clcultor.对于
22、通信(调制/检测)类型、信道衰落模型、分集类型的每一种组合,得到系统的平均误码率(BER)和符号错误率(ER),并以容易求值的形式表示。所有考虑的相应于实际信道的情况,以及许多情况下得到的BER和SR表达式均可用手持计算器来计算。5.Mdlionishe sysemi vriion of som ttrue of a carriwaverm uch as heamplitude, phase, ofrequcyin accodanewit function o the megesignal.It iuse in comnicatin sstems fomthing signl chaactei
23、sticto cannel chacrstcs,oreduin noise andintereren, for smultaneously transittng everlsgnal over sgle hannel, and o vercomng somequnt imations. osrableprtion othisbook is deoteto the stdy f how odlion scme are eineoaciev thabove ss. hescesso a communican stm depends to alage exet on thmodulti.调制是载波波
24、形的某些属性,例如幅度、相位和频率,根据消息信号的函数有规则的变化。它用于通信系统以使信号特性匹配信道特性,减少噪声和干扰,在单个信道上同时传输多个信号,并克服某些设备的限制。本书相当大部分内容是研究如何设计调制方案以实现上述任务。一个通信系统的成功很大程度上依赖于调制。Unit5 Exerises() Traslate the ollong pss noChins.OMconsts o lr uerfsubcrir qually sacd in frequenc bd, ah maye diitallymodlated byasaescheme suh s PS, QAM,.,or b dffrent chemes. A erially transmtted squec is dvied ino a uber of sectons, each having N ybls, ndthe symbols n h ect are se
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