時(shí)間和頻率的基本原理-畢業(yè)設(shè)計(jì)外文翻譯_第1頁
已閱讀1頁，還剩15頁未讀， 繼續(xù)免費(fèi)閱讀

下載本文檔

版權(quán)說明：本文檔由用戶提供并上傳，收益歸屬內(nèi)容提供方，若內(nèi)容存在侵權(quán)，請(qǐng)進(jìn)行舉報(bào)或認(rèn)領(lǐng)

文檔簡(jiǎn)介

1、中北大學(xué)2011屆畢業(yè)設(shè)計(jì)說明書第1頁共16頁外文文獻(xiàn)原文外文文獻(xiàn)原文FundamentalsofTimeFrequencyIntroductionTimefrequencystardssupplythreebasictypesofinfmation：timeofday，timeinterval，frequency.Timeofdayinfmationisprovidedinhours，minutes，seconds，butoftena

2、lsoincludesthedate(month，day，year).Adevicethatdisplaysrecdstimeofdayinfmationiscalledaclock.Ifaclockisusedtolabelwhenaneventhappened，thislabelissometimescalledatimetagtimestamp.Datetimeofdaycanalsobeusedtoensurethatevent

3、saresynchronized，happenatthesametime.Timeintervalisthedurationelapsedtimebetweentwoevents.Thestardunitoftimeintervalisthesecond(s).However，manyengineeringapplicationsrequirethemeasurementofshtertimeintervals，suchasmillis

4、econds(1ms=103s)，microseconds(1μs=106s)，nanoseconds(1ns=109s)，picoseconds(1ps=1012s).Timeisoneofthesevenbasephysicalquantities，thesecondisoneofsevenbaseunitsdefinedintheInternationalSystemofUnits(SI).Thedefinitionsofmany

5、otherphysicalquantitiesrelyuponthedefinitionofthesecond.Thesecondwasoncedefinedbasedontheearth’srotationalrateasafractionofthetropicalyear.Thatchangedin1967whentheeraofatomictimekeepingfmallybegan.Thecurrentdefinitionoft

6、heSIsecondisthedurationof9，192，631，770periodsoftheradiationcrespondingtothetransitionbetweentwohyperfinelevelsofthegroundstateofthecesium133atom.Frequencyistherateofarepetitiveevent.IfTistheperiodofarepetitiveevent，thent

7、hefrequencyfisitsreciprocal，1T.Conversely，theperiodisthereciprocalofthefrequency，T=1f.Sincetheperiodisatimeintervalexpressedinseconds(s)，itiseasytoseethecloserelationshipbetweentimeintervalfrequency.Thestard中北大學(xué)2011屆畢業(yè)設(shè)計(jì)

8、說明書第3頁共16頁necessary，leapsecondsareaddedtoUTConeitherJune30December31.Thepurposeofaddingleapsecondsistokeepatomictime(UTC)within0.9sofanoldertimescalecalledUT1，whichisbasedontherotationalrateoftheearth.Leapsecondshavebeen

9、addedtoUTCatarateofslightlylessthanonceperyear，beginningin1972.KeepinmindthattheBIPMmaintainsTAIUTCas‘‘paper’’timescales.ThemajmetrologylabatiesusethepublisheddatafromtheBIPMtosteertheirclocksoscillatsgeneraterealtimever

10、sionsofUTC.ManyoftheselabatiesdistributetheirversionsofUTCviaradiosignalswhichsection17.4arediscussedin.YoucanthinkofUTCastheultimatestardftimeofday，timeinterval，frequency.ClockssynchronizedtoUTCdisplaythesamehourminute，

11、secondalloverthewld(remainwithinonesecondofUT1).OscillatssimonizedtoUTCgeneratesignalsthatserveasreferencestardsftimeintervalfrequency.TimeFrequencyMeasurementTimefrequencymeasurementsfollowtheconventionsusedinotherareas

12、ofmetrology.Thefrequencystardclockbeingmeasurediscalledthedeviceundertest(DUT).AmeasurementcomparestheDUTtoastardreference.ThestardshouldoutperfmtheDUTbyaspecifiedratio，calledthetestuncertaintyratio(TUR).Ideally，theTURsh

13、ouldbe10：1higher.Thehighertheratio，thelessaveragingisrequiredtogetvalidmeasurementresults.Thetestsignalftimemeasurementsisusuallyapulsethatoccursoncepersecond(1ps).Thepulsewidthpolarityvariesfromdevicetodevice，butTTLleve

溫馨提示

  • 1. 本站所有資源如無特殊說明，都需要本地電腦安裝OFFICE2007和PDF閱讀器。圖紙軟件為CAD,CAXA,PROE,UG,SolidWorks等.壓縮文件請(qǐng)下載最新的WinRAR軟件解壓。
  • 2. 本站的文檔不包含任何第三方提供的附件圖紙等，如果需要附件，請(qǐng)聯(lián)系上傳者。文件的所有權(quán)益歸上傳用戶所有。
  • 3. 本站RAR壓縮包中若帶圖紙，網(wǎng)頁內(nèi)容里面會(huì)有圖紙預(yù)覽，若沒有圖紙預(yù)覽就沒有圖紙。
  • 4. 未經(jīng)權(quán)益所有人同意不得將文件中的內(nèi)容挪作商業(yè)或盈利用途。
  • 5. 眾賞文庫僅提供信息存儲(chǔ)空間，僅對(duì)用戶上傳內(nèi)容的表現(xiàn)方式做保護(hù)處理，對(duì)用戶上傳分享的文檔內(nèi)容本身不做任何修改或編輯，并不能對(duì)任何下載內(nèi)容負(fù)責(zé)。
  • 6. 下載文件中如有侵權(quán)或不適當(dāng)內(nèi)容，請(qǐng)與我們聯(lián)系，我們立即糾正。
  • 7. 本站不保證下載資源的準(zhǔn)確性、安全性和完整性, 同時(shí)也不承擔(dān)用戶因使用這些下載資源對(duì)自己和他人造成任何形式的傷害或損失。

評(píng)論

0/150

提交評(píng)論