《電子信息專業(yè)英語》課件 Lesson 7 Cellphone communication

UnitThree■

主要內(nèi)容：與電子相關(guān)的學(xué)科及領(lǐng)域的知識，如傳感器，計算機(jī)，通信，數(shù)控等等技術(shù)?！鰧W(xué)習(xí)目標(biāo)：了解與電子相關(guān)的學(xué)科及領(lǐng)域的知識，如通信，衛(wèi)星，數(shù)控等方面。■素質(zhì)目標(biāo)：啟發(fā)探索興趣，樹立科學(xué)自信，虛擬交互現(xiàn)實(shí)，增強(qiáng)文化自信；樹立正確的勞動觀，崇尚勞動、尊重勞動、熱愛勞動。Lesson7cellphonecommunicationKeywords■communication[k?,mjuni’kei??n]

通信■antenna[?n’ten?]天線■mobile[’m?ubail]移動的■wireless[’wa??l?s]無線的■wavelength

[’we?v,le?kθ]波長■modulation[,m?dju’lei??n]

調(diào)制■demodulation[’di:,m?dju:’lei??n]

解調(diào)■propagation[,pr?p?’ge???n]

傳播■attenuation[??tenju?ei??n]衰減■spectrum[‘spektr?m]頻譜■transmit[tr?nz’mit]傳輸■phase[feiz]

相位■amplitude[,?mpl?’tu:d]

幅度■amplify[‘?mplifai]

放大■ADC模數(shù)轉(zhuǎn)換器■DAC數(shù)模轉(zhuǎn)換器■工作任務(wù)：如何實(shí)現(xiàn)兩個手機(jī)的通信？■學(xué)習(xí)目標(biāo)：掌握基本的調(diào)制解調(diào)技術(shù)，以及在通信系統(tǒng)中的應(yīng)用?！鲋攸c(diǎn)難點(diǎn)：調(diào)制解調(diào)技術(shù)在各種通信系統(tǒng)中的應(yīng)用■推薦學(xué)時：6學(xué)時■任務(wù)：Howtomakecommunicationoftwomobilephonescometrue？Communications

Toachievewirelesscommunications,antennaisanecessary.Inmobilephone,antennaisverysmalljustlikethis:Fromthepicturewecanseethatthesizeoftheantennaisverysmall.

Asweallknown,thefrequencyofouraudiosignalsis20~200KHZ.Andatthesametime,inordertobetteremittingsignals,thelengthofantennasmustbiggerthan10percentofthewavelengthofsignals.Soifwewanttodirectlyemitaudiosignals,thesizeofantennasishardtothinkforcommonmobilephones.Solution:modulation.modulationisjustspectrumshifting.Thatistosay,modulationistheprocessofshiftingspectrumofonecenterfrquencytoanother.Modulationistheadditionofinformation(orthesignal)toanelectronicoropticalsignalcarrier.Commonmodulationmethodsinclude:Amplitudemodulation(AM),inwhichtheamplitudeofthecarrierisvariedovermodulatesignals.Frequencymodulation(FM),inwhichthefrequencyofthecarrierwaveformisvariedovermodulatesignalsPhasemodulation(PM),inwhichthephaseofthecarrierwaveformisvariedovermodulatesignals.Aftertheemittingofantenna，modulatedsignalstransmitintheair.Generallyspeaking，therearethreepropagationmodes：Sky-wavepropagationLine-of-sightpropagationGround-wavepropagationFig7-5Sky-wavepropagationFig7-6Line-of-sightpropagationFig7-7Ground-wavepropagationBecauseantennaofreceivemobilephonereceivesthesignalswhichareusuallypoor,weshouldamplifythereceivedsignals.Then,changetheanalogsignalstodigtaldatasthroughanADC.Afterthat,weshoulddemodulatethesignals.

Demodulationistheactofextractingtheoriginalinformation-bearingsignalfromamodulatedcarrierwave.TakethedemodulationofAMforexample:microphoneA/DCodingmodulationAntenna1信道噪聲Antenna2AmplifyDemodulaitionDecodin