《电子信息专业英语》课件 Lesson 7 Cellphone communication

UnitThree■

主要内容：与电子相关的学科及领域的知识，如传感器，计算机，通信，数控等等技术。■学习目标：了解与电子相关的学科及领域的知识，如通信，卫星，数控等方面。■素质目标：启发探索兴趣，树立科学自信，虚拟交互现实，增强文化自信；树立正确的劳动观，崇尚劳动、尊重劳动、热爱劳动。Lesson7cellphonecommunicationKeywords■communication[kə,mjuni’keiʃən]

通信■antenna[æn’tenə]天线■mobile[’məubail]移动的■wireless[’waɪəlɪs]无线的■wavelength

[’weɪv,leŋkθ]波长■modulation[,mɔdju’leiʃən]

调制■demodulation[’di:,mɔdju:’leiʃən]

解调■propagation[,prɔpə’geɪʃən]

传播■attenuation[əˌtenjuˈeiʃən]衰减■spectrum[‘spektrəm]频谱■transmit[trænz’mit]传输■phase[feiz]

相位■amplitude[,æmplɪ’tu:d]

幅度■amplify[‘æmplifai]

放大■ADC模数转换器■DAC数模转换器■工作任务：如何实现两个手机的通信？■学习目标：掌握基本的调制解调技术，以及在通信系统中的应用。■重点难点：调制解调技术在各种通信系统中的应用■推荐学时：6学时■任务：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信道噪声Antenna2AmplifyDemodulaitionDecodin