通信与电子信息专业英语 课件 Unit 4 Signals and Systems.pptx

Unit4SignalsandSystems

4.1IntroductiontoSignals

4.2FrequencyResponseofLTISystems

4.3SamplingTheorem

4.1IntroductiontoSignalsWordsandExpressionsBackgroundsText

WordsandExpressionsfunction n.函数variable n.变量Themoderndefinitionoffunctionwasfirstgivenin1837bytheGermanmathematicianPeterDirichlet:Ifavariableyissorelatedtoavariablexthatwheneveranumericalvalueisassignedtox,thereisaruleaccordingtowhichauniquevalueofyisdetermined,thenyissaidtobeafunctionoftheindependentvariablex，symbolizedasy=f(x).4

WordsandExpressionscontinuous-timesignal 连续时间信号discrete-timesignal 离散时间信号5Discrete-timesignalcreatedfromacontinuoussignalby?samplingUnit-StepFunctionunitimpulsefunctionpulsefunction

WordsandExpressionssignaltransformation 信号变换timeshift 时移6

WordsandExpressionsdelay v.滞后advance v.超前7delayedsignal?advancedsignal?

WordsandExpressionsradar n.雷达sonar n.声呐8Radar?(originally?acronym?for?radiodetectionandranging)?isadetectionsystemthatuses?radiowaves?todeterminethedistance(ranging),angle,and?radialvelocity?ofobjectsrelativetothesite.Itcanbeusedtodetect?aircraft,?ships,?spacecraft,?guidedmissiles,?motorvehicles,?weatherformations,and?terrain.?Sonar?(soundnavigationandranging)isatechniquethatuses?sound?propagation(usuallyunderwater,asin?submarinenavigation)to?navigate,measuredistances(ranging),communicatewithordetectobjectsonorunderthesurfaceofthewater,suchasothervessels.

WordsandExpressionsreceiver n.接收机medium n.媒介?propagation n.传播 9AbundleofopticalfiberA?transmissionmedium?isasystemorsubstancethatcanmediatethe?propagation?of?signals?forthepurposesof?telecommunication.

WordsandExpressionstimereversal 时间变量的翻转timescaling 时间变量的尺度变换10

WordsandExpressionsperiodic adj.周期的period n.周期sinusoida