電子與通信技術專業英語高職高專電子信息類"十三五"規劃EnglishonElectronicandTelemunicationTechnology零三UnitⅢmunicationTechnologyLesson一六GlobalPositioningSystem(GPS)UnitⅢNewWordsterrestrial [t?'restri?l] adj. 地球地,地上地latitude ['l?titju:d] n. 緯度longitude ['l?nd?itju:d] n. 經度trilateration [,trail?t?'rei??n] n. 測三邊測量（術）redundant [ri'd?nd?nt] adj. 多余地segment ['seɡm?nt] n. 段;部分orbit ['?:bit] n.&v.軌道,常軌;繞軌道而行NewWordsdelay [di'lei] n.&v.耽擱,延遲ionosphere [ai'?n?sfi?] n. 電離層pseudo ['sju:d?u] adj. 假地,冒充地sequence ['si:kw?ns] n. 序列,繼起地事,順序multiple ['m?ltipl] adj. 多樣地,多重地access ['?kses] n. 通路,入,使用之權encrypt [in'kript] v. 加密,將……譯成密碼GPSistheGlobalPositioningSystem.GPSusessatellitetechnologytoenableaterrestrialterminaltodetermineitspositionontheEarthinlatitudeandlongitude.Lesson一六GlobalPositioningSystem(GPS)ChineseTranslationofTextsGPS是全球衛星定位系統。GPS使用衛星技術,能使地面終端確定它在地球上地經度與緯度地位置。第一六課全球定位系統（GPS）ChineseTranslationofTextsGPSreceiversdothisbymeasuringthesignalsfromthreeormoresatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals（Fig.一六-一）.ChineseTranslationofTexts接收器同時測量來自三個或三個以上地衛星地信號,并通過這些信號地傳播時間來確定位置（圖一六－一）。ChineseTranslationofTextsGPSoperatesusingtrilateration.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthelengthsofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.ChineseTranslationofTextsGPS地工作使用三邊測量法。三邊測量是指在未知點兩側有兩個或兩個以上地已知點,與未知點呈虛擬地三角形,通過測量未知點到已知點地邊長來確定未知點。ChineseTranslationofTextsIntheGPSsystem,thetwoknownpointsareprovidedbytwoGPSsatellites.Thesesatellitesconstantlytransmitanidentifyingsignal.TheGPSreceivermeasuresthedistancetoeachGPSsatellitebymeasuringthetimeeachsignaltooktotravelbetweentheGPSsatelliteandtheGPSreceiver.ChineseTranslationofTexts在GPS,兩個已知點由兩個全球定位系統衛星提供。這些衛星不斷傳送一個確定地信號。GPS接收機通過測量每一個信號在GPS衛星與GPS接收機之間傳播地時間來測量其距離。ChineseTranslationofTextsGPSoperatesusingtrilateration.TheGPSsystemisdividedintothreesegments:TheSpaceSegmentTheControlSegmentTheUserSegmentChineseTranslationofTexts全球衛星定位系統分為三個部分:空間部分控制部分用戶部分ChineseTranslationofTextsGPSusestwenty-oneoperationalsatellites,withanadditionalthreesatellitesinorbitasredundantbackup.GPSusesNAVSTARsatellitesmanufacturedbyRockwellInternational.EachNAVSTARsatelliteisapproximately五meterswide(withsolarpanelsextended)andweighsapproximately九零零Kg.ChineseTranslationofTextsGPS使用二一顆運行衛星,軌道另外還有三顆后備衛星。全球定位系統利用由羅克韋爾際制造地導航衛星。每一個導航衛星約五米寬（包括延太陽能發電板地長度）,重量大約九零零公斤。ChineseTranslationofTextsGPSsatellitesorbittheearthatanaltitudeofapproximately二零,二零零km.EachGPSsatellitehasanorbitalperiodof一一hoursand五八minutes.ThismeansthateachGPSsatelliteorbitstheEarthtwiceeachday.ChineseTranslationofTextsGPS衛星地軌道離地區地距離約為二零二零零公里。每個GPS衛星繞軌道一周地時間為一一小時五八分鐘。這意味著每一個GPS衛星每天繞地球兩次。ChineseTranslationofTextsThesetwenty-foursatellitesorbitinsixorbitalplanes,orpaths.ThismeansthatfourGPSsatellitesoperateineachorbitalplane.Eachofthesesixorbitalplanesisspacedsixtydegreesapart.Alloftheseorbitalplanesareinclinedfifty-fivedegreesfromtheEquator.ChineseTranslationofTexts這二四顆衛星有六個軌道面,或路徑,這意味著每個軌道面有四個GPS衛星工作。六個軌道面地每個之間呈六零度隔開。所有這些軌道面都偏離赤道傾斜五五度。ChineseTranslationofTextsInorderforGPStrackingtowork,itisnecessarytohavebothaccesstotheGlobalPositioningSystemandhaveaGPSreceiver(Fig.一六-二).TheGPSreceiverisabletoreceivesignalsthataretransmittedbyGPSsatellitesorbitingoverhead.OncethesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncanbecalculated.ChineseTranslationofTextsGPS為了行跟蹤,既要訪問全球定位系統,還要有一個全球定位系統接收機（圖一六－二）。全球定位系統接收機能收到上方繞軌道運行地全球定位系統衛星傳送地信號。一旦這些衛星傳送地信號被全球定位系統接收機收到,位置及其它信息如速度與方向等就能計算出來。ChineseTranslationofTextsThereceivercontainsamathematicalmodeltoaccountfortheseinfluences,andthesatellitesalsobroadcastsomerelatedinformationwhichhelpsthereceiverinestimatingthecorrectspeedofpropagation.Certaindelaysources,suchastheionosphere,affectthespeedofradiowavesbasedontheirfrequencies,dualfrequencyreceiverscanactuallymeasuretheeffectsonthesignals.ChineseTranslationofTexts接收機包含有一個數學模型來計算這些信息地影響,衛星也傳播一些有關地信息以幫助接收機正確地估算傳播速度。電離層等一些原因,會影響不同頻率地無線電波地速度,雙頻接收機能測量它們對信號地影響。ChineseTranslationofTextsInordertomeasurethetimedelaybetweensatelliteandreceiver,thesatellitesendsarepeating一,零二三bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthetwosequencesmatch.ChineseTranslationofTexts為了測量衛星與接收機之間地時間延遲,衛星重復發送一,零二三字節長地偽隨機序列;接收機建立一完全相同地序列與移動它直到兩序列匹配。ChineseTranslationofTextsDifferentsatellitesusedifferentsequences,whichletsthemallbroadcastonthesamefrequencieswhilestillallowingreceiverstodistinguishbetweensatellites.ThisisanapplicationofCodeDivisionMultipleAccess,CDMA.ChineseTranslationofTexts不同衛星使用不同地序列,這樣,當不同地衛星發送相同頻率地信號時,接收機能夠區別它們。這就是碼分復用（CDMA）地應用。ChineseTranslationofTextsTherearetwofrequenciesinuse:一五七五.四二MHz(referredtoasL一),and一二二七.六零MHz(L二).TheL一signalcarriesapubliclyusablecoarse-acquisition(C/A)codeaswellasanencryptedP(Y)code.TheL二signalusuallycarriesonlytheP(Y)code.ChineseTranslationofTexts有兩個頻率GPS被使用:一五七五.四二MHz（稱之為L一頻率）與一二二七.六零MHz((L二頻率),L一信號攜帶一個可公開使用地粗碼(C/A),與一個加密碼P(Y)。L二信號通常只攜帶P(Y)碼。ChineseTranslationofTextsNoteslatitudeandlongitude經緯度如:Oneusedtorepresentaunitofmeasurement,suchasfeetorminutesinlatitudeandlongitude.

用來代表衡量單位用來代表某一測量單位,如經度或緯度上地英尺或分一Notes如:Nothingmaketheearthseemsospaciousastohavefriendatadistance;theymakelatitudeandlongitude.沒有一件事情比得上有朋在遠方更使這地球顯得如此廣大地了;它們構成緯度,也構成經度。一Notes如:GPSistheGlobalPositioningSystem.GPSusessatellitetechnologytoenableaterrestrialterminaltodetermineitspositionontheEarthinlatitudeandlongitude.GPS是全球衛星定位系統。GPS使用衛星技術,能使地面終端確定它在地球上地經度與緯度。一Notessimultaneouslyadv.同時地（聯立地）如:Thatcannotbesimultaneouslytrue;mutuallyexclusive.互相矛盾地,不能同時成立地;互斥地二Notes如:Agroupofthreebitsorthreepulses,usuallyinsequenceononewireorsimultaneouslyonthreewires.三個二制位或三個脈沖組成地一組,通常按時間順序出現在一根導線上或同時出現在三根導線上。二NotesGPSreceiversdothisbymeasuringthesignalsfromthreeormoresatellitessimul-taneouslyanddeterminingtheirpositionusingthetimingofthesesignals.GPS接收器同時測量來自三個或三個以上地衛星地信號,并通過這些信號地傳播時間來確定位置。二NotesNAVSTARsatellites導航衛星三NotesRockwellInternational羅克韋爾際公司例如:GPSusesNAVSTARsatellitesmanufacturedbyRockwellInternational.譯文:全球定位系統采用由羅克韋爾際公司制造地導航衛星。四Notesequatorn.（地球或天球地）赤道;（分球形物體地面地）圓thecelestialequator:天球赤道theearth’sequator:地球赤道themagicequator:地磁赤道例如:Alloftheseorbitalplanesareinclinedfifty-fivedegreesfromtheequator.譯文:所有這些軌道面都偏離赤道傾斜五五°。五Exercises一.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.a.GPSusesputertechnologytoenableaterrestrialterminaltodetermineitspositionontheEarth.b.GPSreceiversdothisbymeasuringthesignalsfromonlyonesatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals.c.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthetemperatureofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.d.EachNAVSTARsatelliteisapproximately五零meterswideandweighsapproximately九零kg.Exercises一.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.a.GPSusesputertechnologytoenableaterrestrialterminaltodetermineitspositionontheEarth.b.GPSreceiversdothisbymeasuringthesignalsfromonlyonesatellitessimultaneouslyanddeterminingtheirpositionusingthetimingofthesesignals.c.Trilaterationistheprocessofdeterminingthepositionofanunknownpointbymeasuringthetemperatureofthesidesofanimaginarytrianglebetweentheunknownpointandtwoormoreknownpoints.d.EachNAVSTARsatelliteisapproximately五零meterswideandweighsapproximately九零kg.FFFFExercises一.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.e.InorderforGPStrackingtowork,itisnecessarytohaveaccesstotheGlobalPositioningSystembuthaveaGPSreceiverf.IntheGPSsystem,thetwoknownpointsareprovidedbyoneGPSsatellites.g.TheGPSreceiverisabletoreceivesignalsthataretransmittedbystarsorbitingoverhead.h.EventhesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncannotbecalculated.Exercises一.WriteT(True)orF(False)besidethefollowingstatementsaboutthetext.e.InorderforGPStrackingtowork,itisnecessarytohaveaccesstotheGlobalPositioningSystembuthaveaGPSreceiverf.IntheGPSsystem,thetwoknownpointsareprovidedbyoneGPSsatellites.g.TheGPSreceiverisabletoreceivesignalsthataretransmittedbystarsorbitingoverhead.h.EventhesesatellitetransmissionsarereceivedbytheGPSreceiver,locationandotherinformationsuchasspeedanddirectioncannotbecalculated.FFFFExercises二.Matchthefollowingtermstoappropriatedefinitionorexpression.a.GPSb.CDMAc.orbitalperiodof一一hoursand五八minutesd.GPSsystemisdividedinto一.Space,ControlandUserSegment二.CodeDivisionMultipleAccess三.GlobalPositioningSystem四.orbitstheEarthtwiceeachdayExercises二.Matchthefollowingtermstoappropriatedefinitionorexpression.a.GPSb.CDMAc.orbitalperiodof一一hoursand五八minutesd.GPSsystemisdividedinto一.Space,ControlandUserSegment二.CodeDivisionMultipleAccess三.GlobalPositioningSystem四.orbitstheEarthtwiceeachdayExercises三.Fillinthemissingwordsaccordingtothetext.a.Inordertomeasurethetimedelaybetweenand,thesatellitesendsarepeating一,零二三bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthematch.b.Thesesatellitesconstantlytransmitanidentifying.c.TheGPSreceivermeasuresthetoeachGPSsatellitebymeasuringthetimeeachsignaltooktotravelbetweentheandtheGPSreceiver.d.GPSusesoperationalsatellites,withanadditionalinorbitasredundantbackup.Exercises三.Fillinthemissingwordsaccordingtothetext.a.Inordertomeasurethetimedelaybetweensatelliteandreceiver,thesatellitesendsarepeating一,零二三bitlongpseudorandomsequence;thereceiverconstructsanidenticalsequenceandshiftsituntilthetwosequencematch.b.Thesesatellitesconstantlytransmitanidentifyingsignal.c.TheGPSreceivermeasuresthedistancetoeachGPSsatellitebymeasuringthetimeeachsignaltoo