《专业英语词汇》PPT课件.ppt

专业英语 aerialadj 天线的n 天线e m wave电磁波conveyvt 传递themorsecode莫尔斯电码inacontrolledway有控制的bangn 响声QualityofService服务质量ServiceStatus服务状态 FloatType浮点型 数据 s s b singlesideband单边带reinsertn 重插入takeplace发生allowfor考虑到 允许multiplyv 乘 扩大IntersymbolInterference码间干扰AuxiliaryEquipment辅助设备 inthecaseof在 情况下foresightn 远见looklike看起来象prone to adj 易于 的Payphone付费电话Payload负荷payloadpointers负荷指针Appendix附录 Coverage覆盖CoverageArea覆盖范围 覆盖区 有效区Interference干扰PreliminaryDesign概要设计 初步设计Jam to signalratio干扰信号比Interfererdiversity干扰源分集Interference AdaptiveSystem干扰自适应系统 感应电荷Inductivecharge高保真度音响HighFidelity高层兼容性HighLayerCompatibility高电位差Highpotentialdifference高频HighFrequency HF 高增益天线Highgainantenna高增益功放板HighgainPowerAmplifierboard告警面板Alarmpanel 告警模块Alarmmodule格式转换FormatConversion隔行扫描InterlaceScanning个人编码PersonalNumber个人识别码PersonalIdentityNumber工程手册EngineeringManual工具软件ToolSoftware个人通信网 专用通信网PersonalCommunicationsNetwork 工业水平尺Industrialhorizontalruler工作波长Workingwavelength工作单元workingunit功率分配结构DistributedPowerArchitecture公用密钥 公开密钥Publickey供参考Forreference共享内存SharedMemory共享资源SharedResource 规程Procedure规定容限 可接受容限Tolerance规范和描述语言Specification DescriptionLanguageSDL规则脉冲激励长期预测RegularPulseExcitedLong TermPrediction硅钢片SiliconSteelSheet硅谷SiliconValley硅控整流器SiliconControlRectifier 骨干网BackboneNetwork固定比特率ConstantBitRate固定卫星业务FixedSatelliteServices固定信道分配FixedChannelAllocation固态继电器Solid stateRelay故障 错误fault error failure Bug故障定位Faultlocating故障申告受理FaultComplaintHandling 光探测器Photodetector光开关OpticalSwitch光缆FiberOpticCable光连接器FiberConnectors光滤波器OpticalFilters光敏电阻OpticalResistor光耦合器OpticalCouplers光收发模块OpticalTransceivers 光通道Opticalchannel光网络单元OpticalNetworkUnit光无源器件OpticalPassiveDevices光纤OpticalFiber Opticfiber光纤包层CladdingofFiber国标NationalStandard国际电信联盟InternationalTelecommunicationsUnion国内长途号码NationalTollNumber Ifatransmittingaerialradiatesaconstantamplitudee m waveitconveyslittleinformationtothereceiver transmit发射 传播aerial天线radiate辐射constant常量 不变的amplitude振幅e m wave electromagneticwave电磁波convey传达receiver接收者 接收机 Thesimplestwayofsendinginformationistoswitchthetransmitteronandoffsothataseriesof dotsanddashes aretransmitted themorsecodeforexample Thisisaverycommonmethodofcommunicatingbetweenshipsatsea butitdoesrequiretheoperatorto read thecode switchon off 开 关 aseriesof一连串的morsecode莫尔斯电码operator话务员 Anyprocessofsuperimposingsomepatternonthecontinuouse m wavewhichallowsinformationtobecarriediscalledmodulation Wesaythecarrierwaveismodulated Tomodulateacarrierwaveallweneedtodoistovaryapropertyofthewaveinacontrolledway superimpose迭加modulation调制carrierwave载波property特性 性质inacontrolledway有控制地 Thus ifwevaryitsamplitudeweproduceamplitudemodulation a m ifwevaryitsfrequencyweproducefrequencymodulation f m andifwevaryitsphasewehavephasemodulation p m vary改变amplitude振幅amplitudemodulation a m 调幅frequency频率frequencymodulation f m 调频phase相位phasemodulation p m 调相 Generally interference fromlightingorelectricalmachines producesamplitudedisturbancesonane m wavepassingby 干扰是在光电产品中 伴随着电磁波的传播而产生幅度的干扰Becausetheamplitudeoff m carrierisnotcarryinginformation 调频载波幅度并不承载信息suchinterferencehasverylittleeffectonthereceivedsignal Thisisnotthecasewithana m carrier 但是调幅载波就不一样了 whereallsuchbangsandcracklearedetectedatthereceiveras information interference干扰amplitudedisturbance振幅波动receivedsignal接收信号bang巨响crackle劈啪响 Ontheotherhandthebandwidthofthea m carrierismuchlessthanthatofthef m carrierasweshallnowshow 下面将给出例子 ontheotherhand另一方面bandwidth带宽muchless少得多 Ifwemodulatea100kHzcarrierwitha1kHzsignal itmightbeexpectedthatalthoughthecarrieramplitudewouldmissandfallinstepwiththeamplitudeofthe1kHzsignalthecarrierfrequencywouldremainat100kHz 尽管载波幅度回损失和下降到与 一致 但其频率仍有期望保持在 Infacttwonewfrequencycomponentscanbedetectedinthemodulatedcarrier theyare101kHzand99kHz instepwith与 同步remain保持component成分modulatedcarrier调制波 Thusacarrieroffrequencyfc amplitudemodulatedwithasignaloffrequencyfs当一个载波频率为信号频率为的幅度信号调制包含三个频率containsfrequenciesfc fc fs fc fs Thelasttwoarecalled sidebands Fig 5 1isthefrequencyspectrumofana m carrier sideband边带frequencyspectrum频谱a m carrier调幅载波 Fig 5 1Thecarrierandsidebandsofana m signal The carrier componentremainsatconstantamplitudeandisnotconveyinginformation exceptaboutitsownfrequency 载波的成分保持在一个固定的幅度且并不传播信息Itrepresents wasted transmitterpower Sometimesitisnotradiated没有辐射 thenwehavea suppressedcarriera m transmission 抑制Sometimesonlythecarrierandonesidebandareradiated sometimesonlyonesideband s s b singles b represent表明wasted浪费 消耗suppress抑制transmission传输 Iflessthanthefulla m carrier完全振幅调制载波istransmittedthereceiverneedstobemorecomplicatedtoreceiveit 接收非常复杂becausebasicallythecarriermustbereinsertedatthereceiverbeforedetectioncantakeplace 在检波前要重新再植入一个载波 lessthan小于complicated复杂的reinsert重新插入detection检波 Ina m thefullbandwidth在振幅调制里一个完全的带宽isfromfc fstofc fs i e 2fssothatforaspeechtransmissionwherevoicefrequenciesextendupto3kHz weshouldneed6kHzofbandwidth formusic30kHzneeded bandwidth带宽i e 也就是speechtransmission音频传输extendupto增加到 Transmittersshouldbespacesapartinfrequencytoallowforthesebandwidthrequirements Thereareinternationalagreementsaboutfrequenciesbuttheyarenotobservedbyallcountries transmitter发射机spaceapart空间分离allowfor虑及 考虑到bandwidthrequirement带宽要求internationalagreement国际协议observe遵守 Forthemathematicallyinclineditiseasytoshowthatthesinusoidalmodulationoftheamplitudeofasinusoidalwave formresultsintheproductionofsumanddifferencefrequencies inclined倾向sinusoidalmodulation正弦调制sinusoidalwave form正弦波形resultin导致 体现 Supposewehaveanun modulatedcarrier fc oftheforma Asin 2 fct whereaistheinstantaneousamplitudeandAisthemaximumamplitude oftensimplyreferredtoastheamplitudeofthecarrier NowletusmodulateAsinusoidallyatafrequencyfs andwrite suppose假设un modulated未调制instantaneousamplitude瞬时值maximumamplitude最大值sinusoidally正弦地 a A 1 ksin 2 fst sin 2 fct kisaconstantmultiplyingoutwegeta Asin 2 fct Aksin 2 fst sin 2 fct Asin 2 fst AK 2 cos 2 fc fs t cos 2 fc fs t carrier AK 2 lowersideband uppersideband multiplyout乘lowersideband下边带uppersideband上边带 Whenkis1wehave100 modulation forthetwosidebandseachofamplitudeA 2cancombinetomakethetotalamplitudevaryfromzeroto2A for 引导原因状语从句 Whenkis1 是时间状语从句 eachofamplitudeA 2 则是后置定语 修饰 sideband Inthecaseoff m amathematicalanalysisofthemodulatedcarrierismoredifficultthanfora m andwouldinvolveusinBesselfunctions mathematicalanalysis数学分析modulatedcarrier 已 调制载波Besselfunctions贝塞尔方程involvein涉及 Besselwasanineteenthcenturymathematicianwhohadtheforesighttosolvetheveryequationsweneedforf m Sowe