lecroy 22_LTXXX-OM-E_Glossary 电路图.pdf

《lecroy 22_LTXXX-OM-E_Glossary 电路图.pdf》由会员分享，可在线阅读，更多相关《lecroy 22_LTXXX-OM-E_Glossary 电路图.pdf（12页珍藏版）》请在收音机爱好者资料库上搜索。

1、LTXXX-OM-E Rev BISSUED: January2002243 GL O S S A R YO FTE C H N I C A LTE R M S AcquisitionTime: Inasample-and-holdor track-and-holdcircuit, thetimerequiredafter thesampleor track commandfor theoutput toslewthroughafull-scalevoltagechangeandsettletoits final valuewithina specifiederror band. ACSN:

2、auto-correlationsignal-to-noise ADC: analog-to-digital converter. Aliasing: Whenever adynamic signal is synchronouslysampled, apossibilityof misunderstandingits frequency content exists. This difficultyis termed“aliasing” andoccurs whenever thesamplingrateis less than twicethe highest frequencycompo

3、nent inthesignal beingmeasured. AND: Logical designation or circuit functionmeaningthat all inputs must beintheTRUE statefor aTRUE output. Aperture Jitter: Inasample-holdor ADC, thejitter betweenthetimeof thesample(or convert)command pulseandthetimetheinput signal is actuallysampled. This jitter is

4、usuallyduetothermal noise. It leads toan uncertaintyinthesampledamplitudeequal todeltat*dV/dt, wheredeltat is theaperturejitter, anddV/dt is therateof changeof theinput voltageat thetimeof sampling. Theterms “aperturejitter” and“aperture uncertainty” areoftenusedinterchangeably. Aperture Uncertainty

5、: Inasample-holdor ADC, thetotal uncertaintyinthetimeof thesample(or convert) commandpulseandthetimetheinput signal is actuallysampled, duetoall causes includingnoise, signal amplitude-dependent delayvariation(as inaflashADC), temperature, etc. Oftenusedinterchangeablywith “aperturejitter,” but “ape

6、rtureuncertainty” is themoreinclusiveterm. Area: InatimedomainDSO waveform measurement, areais thesum of thesampledvalues betweenthe cursors times thedurationof asample. Artifact Rejection: Usedinsummedaveragingtoexcludewaveforms that haveexceededthedynamic rangeof therecordingsystem. Automatic Setu

7、p: Inanoscilloscope, automatic scalingof thetimebase, trigger, andsensitivitysettings. Provides astabledisplayof repetitiveinput signals. Average: SeeMeanValue, SummedAveragingandContinuous Averaging. AWG: arbitrarywavegenerator Bandwidth: Innormal use, thefrequencyrangeover whichthegainof anamplifi

8、er or other circuit does not varybymorethan3 dB. BER: SeeBit Error Rate. Binning: A techniquefor combiningpoints inahistogram tobecompatiblewiththeresolutionof thedisplay device. Bit: Anabbreviationof “binarydigit,” oneof thetwonumbers, 0 and1, usedtoencodedata. A bit is often expressedbyahighor low

9、electrical voltage. RadioFans.CN 收音机爱 好者资料库 GL O S S A R Y 244ISSUED: January2002LTXXX-OM-E Rev B Bit ErrorRate: Ratioof thenumber of bits of amessageincorrectlyreceivedtothetotal number received. CCD: ChargeCoupledDevice. Anintegratedcircuit that allows thetransfer of avariableamount of charge thro

10、ughaseries of cells; ananalogshift register. CCTM: clockcertificationtest module Channel: A paththroughanarrangement of components (modules andelectrical or optical cablingor both) alongwhich signals canbesent. Clamping: Holdingacircuit point tosomereferencelevel (frequentlyground)bymeans of alow-im

11、pedance element suchas asaturatedtransistor, FET, forward-biaseddiode, relay, etc. Coherent Gain: Thenormalizedcoherent gain of afilter correspondingtoeachwindowfunctionis 1.0 (0 dB) for therectangular windowandless than1.0 for other windows. It defines theloss of signal energyduetothe multiplicatio

12、nbythewindowfunction. CommonMode Range: Themaximum range(usuallyvoltage)withinwhichdifferential inputs canoperate without aloss of accuracy. CommonMode RejectionRatio: Theratio of thecommon-modeinput voltagetotheoutput voltage expressedindB. Theextent towhichadifferential amplifier does not providea

13、noutput voltagewhenthesame signal is appliedtobothinputs. CommonMode Signal(Noise): Thesignal (usuallynoise)that appears equallyandinphaseoneachof the differential signal conductors toground. SeeDifferential Input. Continuous Averaging: Sometimes called“exponential averaging,” thetechniqueconsists o

14、f therepeated addition, withunequal weight, of successivesourcewaveforms. Eachnewwaveform is addedtothe accumulatedaverageaccordingtotheformula: S(i,new)= N/(N+1)* S(i,old)+ 1/(N+1)* W(i) wherei = indexover all datapoints of thewaveforms; W(i)= newlyacquiredwaveform;S(i,old)= oldaccumulated average;

15、 S(i,new)= newaccumulatedaverage; N = weightingfactor (1,3,7.). ConversionCycle: Entiresequenceinvolvedinchangingdatafrom oneform toanother, e.g.,digitizingan analogquantity, changingbinarydatatoBCD, etc. Crosstalk: Unwantedcouplingof asignal from onechannel toanother. Cursor: A visiblemarker that i

16、dentifies ahorizontal or vertical position, or both, onan oscilloscopedisplay. LeCroyDSOs offer “waveform riding” cursors that convenientlygiveboth thehorizontal andvertical values without selectingoneor theother. DAC: digital-to-analogconverter Data Logger: Aninstrument that accepts input signals (

17、usuallyslowanalog), digitizes them, andstores the results inmemoryfor later readout. Thedigital equivalent of astrip-chart recorder. DC: Direct current. Normallymeans avoltageor current that remains constant. DC LevelShift: A changeinthenominal DC voltagelevel present inacircuit. DC Offset: SeeDC Le

18、vel Shift. This term mayimplythat theshift is intentional, for example, adjustablebya control knob. RadioFans.CN 收音机爱 好者资料库 TechnicalTerms LTXXX-OM-E Rev BISSUED: January2002245 DC Overload: Anoverloadsignal of longdurationcomparedtothenormal input pulsewidthor dutyratioof acircuit. Dead Time: Inadi

19、gital oscilloscope, thedeadtimeis thetimefrom theendof oneacquisition of datatothe start of thenext acquisition. Decimation: Theprocess of reconstructingasourcewaveform withareducednumber of datapoints byusing onlyeverynthdatapoint, wherenis aninteger. DifferentialInput: A circuit withtwoinputs that

20、 is sensitiveto thealgebraic differencebetweenthetwo. DifferentialLinearity: A term ofteninappropriatelyusedtomeandifferential non-linearity. DifferentialNon-Linearity: 1. Thepercentagedeparturefrom theaverageof theslopeof theplot of output versus input from theslopeof areferenceline; 2. Thepercenta

21、geof variationin ADCs or TDCs from the meanof theanalog(or time)widthof anysingledigital step. It is usuallymeasuredbydrivingtheinput witha largenumber of random amplitudepulses andthenmeasuringtherelativenumber of events ineachdigital bin. DifferentialOutput: A circuit withtwo outputs supplyingonen

22、ormal andonecomplementarylevel of output signal. DifferentialPulses: Twooppositepolaritypulses coincident in time. Dithering: Typicallyusedwhenaveragingsignals (which havelownoisecontent)toimprovevertical resolution anddecreasetheeffects of anADCs non-linearities. Thetechniqueapplies different offse

23、ts toeachincoming waveform toensurethesignal is not always digitizedbythesameportionof theADC. Theoffsets must be subtractedfrom therecordedsignals beforebeingincludedinthesummedaverage. DigitalFiltering: Themanipulation of digital datatobothenhancedesirableandtoremoveundesirable aspects of thedata.

24、 Dropout Trigger: A trigger that occurs if theinput signal drops out for atimeperiodlonger thanapreset amount (between25 ns to20 s onsomeLeCroyDSOs). This is veryuseful for triggeringonmicroprocessor crashes, networkhangups, bus contentionproblems or other phenomenawhereasignal stops occurring. Duty

25、Cycle: A computedvalueindigital scopes representingtheaveragedurationabovemidpoint valueas a percentageof theperiodfor timedomainwaveforms. Dynamic Range: Theratioof thelargest tosmallest signal that canbeaccuratelyprocessedbyamodule. Dynamic RAM (DRAM): A random access memoryinwhichtheinternal memo

26、rymust berefreshed periodically. ECL: Emitter-coupledlogic, anunsaturatedlogic performedbyemitter-coupledtransistors. Usually, ECL LOGICAL 1 = 1.6 V andLOGICAL 0 = 0.8 V. EMI: Electromagnetic interferencecausedbycurrent or voltageinducedintoasignal conductor byan electromagnetic field. ENBW (Equival

27、ent Noise Bandwidth): For afilter associatedwitheachfrequencybin, ENBW is the bandwidthof anequivalent rectangular filter (havingthesamegainat thecenter frequency)that wouldcollect thesamepower from awhitenoisesignal. RadioFans.CN 收音机爱 好者资料库 GL O S S A R Y 246ISSUED: January2002LTXXX-OM-E Rev B Enha

28、nced Resolution(ERES): A facilityinLeCroyDSOs toincreasetheamplituderesolutionof single-shot waveform measurements. This technique, whichapplies digital filteringtoachieveresolutionenhancement at a reducedbandwidth, is optimum whenthesamplingrateof theinstrument exceeds that requiredfor theinput sig

29、nal bandwidth. For repetitivesignals, either ERES or Signal Averaging, or both, can beusedtoachieve higher resolutionwithsubstantiallysmaller loss of bandwidththanfor single-shot signals. Envelope: Themaximum, minimum, or maximum andminimum values of asequenceof measured waveforms. InLeCroyDSOs, the

30、number is programmablefrom 1 to106. EPROM: Erasable, programmableread-onlymemory. Anintegratedcircuit memoryarraythat is madewitha patternof either all logical zeros or ones andhas apatternwrittenintoit bytheuser withaspecial hardware program. Equivalent Time Sampling (EQT): (Alsoknownas ETS.)A mean

31、s of exploitingmultipleacquisitions of a repetitivesignal toincreasetheusablebandwidthof adigitizer bymakingit appear to samplemorerapidlythan its maximum single-shot samplerate. Works onlywith stable, repetitivesignals. Extrema: Thecomputationof awaveform envelope, byrepeatedcomparison of successiv

32、ewaveforms, of all maximum points (roof)andall minimum points (floor). Whenever agivendatapoint of thenewwaveform exceeds thecorrespondingmaximum valueintheroof record, it is usedtoreplacetheprevious value. Whenever agivendatapoint of thenewwaveform is smaller thanthecorrespondingfloor value, it is

33、usedto replacetheprevious value. Falltime: Unless otherwisedefined, thetimerequiredfor apulsetogofrom 90 % to10 % of full amplitude. Canalsorefer generallytothetrailingedgeof apulse. Fast FourierTransform(FFT): Insignal processingapplications, anFFT is amathematical algorithm that takes adiscretesou

34、rcewaveform, definedover npoints, andcomputes ncomplexFourier coefficients, which areinterpretedas harmonic components of theinput signal. For a“real” sourcewaveform (imaginarypart equals 0), therearen/2 independent harmonic components. Feedthrough: Anunwantedsignal that passes aclosedgateor disable

35、dinput. FFT: SeeFast Fourier Transform. FFT FrequencyBins: A Fast Fourier Transform (FFT)corresponds toanalyzingtheinput signal withabank of n/2 filters, all havingthesameshapeandwidth, andcenteredat n/2 discretefrequencies. Eachfilter collects thesignal energythat falls intotheimmediateneighborhood

36、of its center frequency, andthus it canbesaidthat therearen/2 “frequencybins.” Thedistance, inHz, betweenthecenter frequencies of twoneighboringbins is always: deltaf = 1/T, whereT is thedurationof thetime-domainrecords inseconds. Thenominal widthof binis equal todeltaf. FFT FrequencyRange: Therange

37、of frequencies computedanddisplayedinanFFT is 0 Hz totheNyquist frequency. FFT FrequencyResolution: Inanarrowsense, thefrequencyresolutionis equal tothebin width, deltaf. That is, if theinput signal changes its frequencybydeltaf, thecorrespondingspectrum peakwill bedisplaced bydeltaf. For smaller ch

38、anges of frequency, onlytheshapeof thepeakwill change. However, theeffective frequencyresolution(i.e., theabilitytoresolvetwo signals whosefrequencies arealmost thesame)is further TechnicalTerms LTXXX-OM-E Rev BISSUED: January2002247 limitedbytheuseof windowfunctions. TheENBW valueof all windows oth

39、er thantherectangular is greater thandeltaf (i.e., greater thanthebinwidth). FFT Numberof Points: FFT is computedover thenumber of points (Transform Size)whoseupper bound is thesourcenumber of points. FFT generates spectrahavingn/2 output points. FFT TotalPower: Areaunder thepower densityspectrum in

40、frequency-domainmeasurements. FIFO: First-in, first-out shift registers (sometimes calledfirst-in, first-out memory). Filter: Anelectronic circuit or digital datamanipulationroutinethat either enhances desirableor removes undesirableaspects of ananalogwaveform or its digital representation. Filters

41、areusedtoblockspecific frequencycomponents from passingthroughacircuit, tolinearizeotherwiseidentical components (suchas CCDs)usedinacommoncircuit, or to perform waveform integration, differentiation, or smoothing, just to nameafewtypes. FlashADC: A veryfast analog-to-digital converter, usuallyconsi

42、stingof alargeset of fast comparators and associatedlogic, inwhichtheanalogsignal simultaneouslyis comparedto2n 1 different referencevoltages, wherenis theADC resolution. Alsocalledaparallel converter. Floor: Therecordof points that makethebottom (or minimum)of anenvelopecreatedfrom asuccessionof wa

43、veforms. FWHM: Full-WidthHalf Maximum. Thewidthof apulseor waveform at 50 % amplitudeusedtomeasure thedurationof asignal. Gate: 1. A circuit element usedtoprovidealogical function(e.g., AND, OR); 2. Aninput control signal or pulseenablingthepassageof other signals. Glitch: A spikeor short-timedurati

44、onstructural aberrationonan otherwisesmooth waveform that is normally characterizedbymoregradual amplitudechanges. Indigital electronics, wherethecircuit under test uses an internal clock, aglitchcanbeconsideredtobeanypulsenarrower thantheclockwidth. GlitchTrigger: A trigger on pulsewidths smaller t

45、hanagivenvalue. Ground Loop: A longgroundconnectionalongwhichvoltagedrops occur dueeither toheavycircuit current or external pick-up, withtheresult that circuit elements referredtodifferent points alongit operateat different effectivegroundreferences. HF Sync: Reduces thetrigger ratebyincludingafreq

46、uencydivider inthetrigger path, enablingtheinput trigger ratetoexceedthemaximum for repetitivesignals. Histogram: A graphical representation of datasuchthat thedatais dividedintointervals or bins. Theintervals or bins arethenplottedonabar chart wheretheheight is proportional tothenumber of datapoint

47、s contained ineachinterval or bin. Holdoff byEvents: Selects aminimum number of events betweentriggers. Anevent is generatedwhen the trigger sourcemeets its trigger conditions. A trigger is generatedwhen thetrigger conditionis met after the selectednumber of events from thelast trigger. Thehold-off

48、byevents is initializedandstartedoneach trigger. GL O S S A R Y 248ISSUED: January2002LTXXX-OM-E Rev B Holdoff byTime: Selects aminimum timebetweentriggers. A trigger is generatedwhenthetrigger condition is met after theselecteddelayfrom thelast trigger. Thetimingfor thedelayis initializedandstarted

49、oneach trigger. HPGL: Hewlett-PackardGraphics LanguageFormat; Hewlett-PackardCompany. Hybrid Circuit: A small, self-contained, high-densitycircuit element usuallyconsistingof screenedor depositedconductors, insulatingareas, resistors, etc., with weldedor bondedcombinations of discretecircuit elements andintegratedcircuit chips. IC: IntegratedCircuit. A self-contained, multiple-element circuit suchas amonolithic or hybrid. IntegralLinearity: A term oftenusedinappropriatelytomeanintegral non-linearity. IntegralNon-Linearity: Deviation of ADC responsefrom anappropriatestraight linefit. The