简述移动通信系统中发信机的主要作用。
答：发信机的主要作用是将所要传送的信号首先对载波信号进行调制，形成已调载波，已调载波信号经过变频(有的发射机不经过这一步骤)成为射频载波信号送至功率放大器，经功率放大器放大后送至天馈线。
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PartIVTranslation
Tocoverthemarksofthefire,thebuildingwaspaintedwhite.BeforelongitbecameknownastheWhiteHouse.(PassageOne)
PartIVTranslation
Yetthesecarcinogenicadditivesremaininourfood,anditbecomesmoredifficultallthetimetoknowwhichthingsonthepackaginglabelsofprocessedfoodarehelpfulorharmful.(PassageTwo)
Passage1
Questions1to5arebasedonthefollowingpassage:
DoyouwanttosaywhatyouthinkinalettertothePresidentoftheUnitedStates?You’llgetareplyfromhim—writteninink,nottyped—afteronlyafewdays.
ThePresidentgetsabout4,000letterseveryweek.HeanswerseveryonewhowritestohimonspecialWhitesHousepaper.Buthedoesn’tneedalotoftimeforit.Infact,heonlygives20minutesaweektolookathispersonalcorrespondence.Hehasthemostmodernsecretaryintheworldtohelphim.
It’scomputer,worth￡800，000，whichhasitsownroomsonthefirstflooroftheWhiteHouse.IthasabankofelectronicpenswhichwritelikethePresidentwrites,inhisfavoritelightblueink.EachletterthePresidentreceivesgetsanumber,accordingtothetypeofansweritneeds.Thepensthenwritethecorrectreplyforit,accordingtothenumber.Eachlettertakeslessthanasecondtowrite.AWhiteHouseofficialsaid,“It’snotimportantthatletterscomefromacomputer.EachlettersayswhatthePresidentwantstosay.”
1.forareplyfromthePresident.
A.YouhavetowaitalongtimeB.Youonlyhavetowaitseveraldays
C.YouhavetowaitatleastonemonthD.Youonlyhavetowaitafewweeks
2.ThereplyfromthePresident.
A.isalwaysprintedB.isalwaystyped
C.isalwayswrittenininkD.isalwayswrittenbyhimself
3.Ittakesthecomputertowritetenletters.
A.nomorethantensecondsB.alittlemorethantenseconds
C.lessthantensecondsD.atleastonesecond
4.Thecomputercanbedescribedas.
A.expensivebutefficientB.possessingabeautifulhandwriting
C.heavyandinefficientD.thePresident’smostreliablesecretary
5.Itcanbeinferredfromthepassagethat.
A.thePresidentneverreadsanyletterswrittentohimbyordinarypeople
B.thePresidenthiresaveryefficientsecretarytodealwithhiscorrespondence
C.thePresidentdoesnotreallycareaboutthelettershereceiveseveryweek
D.thePresidentisassuredthatthecomputerexpresshisviewsintheletters
医患沟通中言语形式的交流不包括
PartIVTranslation
Notmanyofthechildrenoffertheirfatherssomepresents.ButtheAmericanfathersstillthinktheyaremuchbetterfatedthanthefathersofmanyothercountries,whohavenotevenadayfortheirsakeinnameonly.(PassageThree)
