信号发生器的基本知识概述

1、Source BasicsCopyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource BasicsCopyright 2000Sources Generate Sine WavesVoltageTimeVoltageFrequencyThis is the ideal output: most specs deal with deviations from the ideal and adding modulation to a

2、sine waveRFMicrowaveMillimeter20-50 GHz300 GHz3-6 GHzSpectrum AnalyzerOscilloscopeSource BasicsCopyright 2000Types of SourceslCWgenerates a single frequency, fixed sine wavelSweptsweeps over a range of frequenciesmay be phase continuouslSignal Generatoradds modulationproduces “real world” signalSour

3、ce BasicsCopyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource BasicsCopyright 2000CW Source Specifications.FrequencyVoltageFrequencyUncertaintylRange: Range of frequencies covered by the sourcelResolution: Smallest frequency increment.lAccu

4、racy: How accurately can the source frequency be set.EXAMPLEAccuracy = =CW frequency = 1 GHz=aging rate = 0.152 ppm/year=time since last calibrated = 1 year +_fCWtagingcalt*fCWtagingcaltAccuracy = 152 Hz+_Source BasicsCopyright 2000CW Source Specifications.AmplitudeDUTSource protected from accidenta

5、l transmission from DUTVoltageFrequencyHow accurate is this number?What is P out?What is P out?maxminlRange (-136dBm to +13dBm)lAccuracy (+/- 0.5dB)lResolution (0.02dB)lSwitching Speed (25ms)lReverse Power ProtectionSource BasicsCopyright 2000lPhase NoiselResidual FMlSpuriousCW Source Specifications

6、.Spectral Puritynon-harmonic spur65dBcharmonic spur30dBcCW outputResidual FM is the integrated phase noise over 300 Hz - 3 kHz BWphase noise 0.5 f0 f0 2f0sub-harmonicsSource BasicsCopyright 2000CW Source Specifications. Spectral Purity: Phase NoiseCW outputfrequencyPower Spectral Densitymeasured as

7、dBc/HzCh1 PM PSD1k10k100kTRACE A:A Marker 10 000 Hz75 dBc/Hz-125 dBc/HzLogMag 5 dBc/div-105 dBc/HzSource BasicsCopyright 2000RF CW Block DiagramReferenceOscillatorfVCOPhaseDetectorFrac-Ndivideby XALC ModulatorALCDriverALC DetectorOutputAttenuatorALC = automatic level controlReference SectionSynthesi

8、zer SectionOutput SectionSource BasicsCopyright 2000RF CW Block DiagramReference SectionfPhaseDetectorOptional External Reference InputReference Oscillator (TCXO or OCXO) TCXOOCXOAging Rate+/- 2ppm/year+/- 0.1 ppm /yearTemp.+/- 1ppm+/- 0.01 ppmLine Voltage+/- 0.5ppm+/- 0.001 ppmto synthesizer sectio

9、ndivideby XSource BasicsCopyright 2000RF CW Block DiagramSynthesizer SectionfVCOPhaseDetectorFrac-Nfrom reference sectionto output sectionX 2multiplierFront panelcontrol5MHz465.5 MHzN = 93.1931 MHz5MHduces accurate, clean signalsSource BasicsCopyright 2000RF CW Block DiagramSynthesizer Sectionr

10、eferenceoscillatorphase noise of sourceVCO noisephase detector noisebroadband noise floor20logNphase-locked-loop (PLL) bandwidth selected for optimum noise performancePLL / Fractional - N.suppresses phase noisefrequencynoiseSource BasicsCopyright 2000RF CW Block DiagramOutput SectionALC = automatic

11、level controlALC ModulatorALCDriverALC DetectorOutputAttenuatorfrom synthesizer sectionsource outputlALCmaintains output power by adding/subtracting power as neededlOutput Attenuatormechanical or electronicprovides attentuation to achieve wide output range (e.g. -136dBm to +13dBm)Source BasicsCopyri

12、ght 2000mWave CW Block DiagramALC DetectorALC ModulatorALCDriverOutputAttenuatorSamplerReference SectionSynthesizer SectionOutput SectionRef OscfVCOPhaseDetFracNby XfVCOPhaseDetectorFrac-NfPhaseDetectorTuningCoilsYIGOscillatorSource BasicsCopyright 2000Applications & Critical SpecificationslLoca

13、l Oscillatorphase noisefrequency accuracylAmplifier DistortionspuriousTOI (for system)lReceiver TestingSpurious spurious level accuracySource BasicsCopyright 2000Applications & Critical SpecificationsAs a Local OscillatorIF signaltransmitter outputpoor phase noise spreads energy into adjacent ch

14、annelspoor frequency accuracy will cause transmitter to be at the wrong frequencyDUTSource BasicsCopyright 2000Applications & Critical SpecificationsAmplifier Testingf2f1fU = 2f2 - f1fL = 2f1 - f2spurious signals from source can corrupt measurementfrequencyamplitudetest system third order produc

15、ts will also fall hereoutput RFisolatorf1f2DUTIntermodulation DistortionSource BasicsCopyright 2000Applications & Critical SpecificationsReceiver TestingIF Rejection CurveFrequencyLevel (dBm)spur from source and/or high levels of phase noise can cause a good receiver to failsource outputIF signa

16、lin-channel signal(modulated signal)out-of-channel signal(CW or modulated signal)DUTReceiver SelectivitySource BasicsCopyright 2000Agilent Families of CW GeneratorsRFMicrowaveAgilent 8664/65 familyl 100 MHz - 6 GHzl Low out channel noisel AM/FM/Pulse.Agilent 8662/63 familyl 100 KHz - 2.5 GHzl Low in

17、 channel noisel AM/FM/Phase/PulseAgilent 83711/12B familyl 10 MHz - 20 GHzl CW onlySource BasicsCopyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource BasicsCopyright 2000Sweeper Specifications.Frequencylramp sweepaccuracysweep timeresolution

18、lstep sweepaccuracynumber of pointsswitching timetimefrequencyf2t2t1f1t4t3t1t2f4f3f1f2frequencySource BasicsCopyright 2000Sweeper Specifications.AmplitudeFrequency SweeplLevel AccuracylFlatnesslSource Match (SWR)Power SweeplPower Sweep RangelPower Slope RangelSource Match (SWR)flatness speclevel acc

19、uracy specf1f2frequencypowerpowerP2P1power sweep ranget1t2Source BasicsCopyright 2000Applications & Critical SpecificationslFrequency ResponseFrequency AccuracyOutput Power (Level) AccuracyFlatnessSpeedresidual FMlAmplifier CompressionPower RangeSource BasicsCopyright 2000Applications & Crit

20、ical SpecificationsFrequency Response TestingLOSweeper InputlFrequency AccuracylOutput Power (Level) AccuracylFlatnesslSpeedlresidual FMSource BasicsCopyright 2000Applications & Critical SpecificationsFrequency Response TestingCenter 2 450.212 MHz Span 1 099.577 MHz11356 BW: 429.600 MHz CF: 2405

21、.782 MHz Q: 5.60Loss: -0.84 dB1:TransmissionLog Mag 5.0 dB/Ref -15.00 dB -35 -30 -25 -20 -10 -5 0 5AbsdB Ch1Who Cares About Accuracy?Source BasicsCopyright 2000Applications & Critical SpecificationsAmplifier CompressionPower InPower Out1 dB compressionpointThe 1 dB compression point is a common

22、amplifier specification used to identify the linear operating range of an amplifier. Power sweep is available on some Agilent sources.lPower RangeSource BasicsCopyright 2000Synthesized Sweep Generators6Agilent 83750 Series Step/Analog sweepAM/FM/Phase modulation 10MHz to 20GHzup to 110GHz with 83550

23、 series modules and amplifier 6Agilent 8360L Series Step/Analog sweep8510/8757 Compatibility 10MHz to 50GHzup to 110GHz with 83550 series modulesSource BasicsCopyright 2000AgendalTypes of sourceslCWlSweptlSignal GeneratorlBlock DiagramslApplicationslSpecificationsSource BasicsCopyright 2000Signal Ge

24、neratorslCalibrated modulationAnalog (AM, FM, PM, Pulse)Digital (I-Q)Format Specific(TDMA,CDMA, etc.)Source BasicsCopyright 2000Modulation.Where the information residesAM, PulseFMPMqV= A(t) sin (t)pV= A(t) sin2 f(t) + (t)fSource BasicsCopyright 2000Modulation: AnalogAmplitude ModulationImportant Sig

25、nal Generator Specs for Amplitude ModulationVoltageTimeCarrierModulationlModulation frequencylLinear AMlLog AMlDepth of modulation (Mod Index)Source BasicsCopyright 2000Modulation: AnalogFrequency ModulationVoltageTimeImportant Signal Generator Specs for Frequency ModulationV= A sin2 f t + m(t)pcbF

26、/Fdevmodb = DlFrequency DeviationlModulation FrequencyldcFMlAccuracylResolutionSource BasicsCopyright 2000Modulation: AnalogPhase Modulationb = Df peakV= A sin2 p f t + m(t)Important Signal Generator Specs for Phase ModulationlPhase deviationlRateslAccuracylResolutionVoltageTimecbSource BasicsCopyri

27、ght 2000Modulation: AnalogPulse ModulationTimePulseOn/Off ratioRisetimeRate=1/TTWidthPowert1/t1/TPowerImportant Signal Generator Specs for Pulse ModulationlPulse widthlPulse periodlOn/Off ratiolRise timeSource BasicsCopyright 2000Digital Modulation.signal characteristics to modifyAmplitudeFrequency

28、PhaseBoth Amplitudeand PhaseSource BasicsCopyright 2000Digital ModulationPolar Display: Magnitude & Phase Represented TogetherlMagnitude is an absolute valuelPhase is relative to a reference signalPhaseMag0 degSource BasicsCopyright 2000Digital ModulationSignal Changes or ModificationsPhaseMag0

29、degMagnitude ChangePhase0 degPhase ChangeFrequency ChangeBoth Change0 deg0 degSource BasicsCopyright 2000Digital Modulation.Binary Phase Shift Keying (BPSK)fV= A sin2 ft + (t) (t) =f1f2pfSource BasicsCopyright 2000Digital ModulationBPSK IQ DiagramIQ01One Bit Per SymbolSymbol Rate = Bit RateSource Ba

30、sicsCopyright 2000Digital Modulation.Quadrature Phase Shift Keying (QPSK)V= A sin2 ft + (t)f (t) =f1 = 3 /4pf2 = /4pf3 = - /4pf4 = - 3 /4ppfSource BasicsCopyright 2000Digital ModulationQPSK IQ DiagramIQ00011011Source BasicsCopyright 2000Digital Modulationp/4 DQPSK IQ DiagramIQSource BasicsCopyright

31、2000Digital ModulationModulation AccuracyIQMagnitude Error (IQ error mag)Error VectorIdeal (Reference) SignalPhase Error (IQ error phase)TestSignalf fSource BasicsCopyright 2000Digital Signal Generator Block DiagramIQ Modulatormodulation qualityBaseband Generatormodulation qualityadjacent channel pe

32、rformancesupported modulation formatsreference section (supplies timing)to output sectionSource BasicsCopyright 2000Digital ModulationPSK Implementation: IQ Methodp p/2CarrierlGood Interface with Digital Signals and CircuitslCan be Implemented with Simple CircuitslCan be Modified for Bandwidth Effic

33、iencyI:Q:Source BasicsCopyright 2000Digital Signal Generator Block DiagramIQ Modulatorp p/2DACDACExt IExt Qfrom synthesizer sectionto output sectionQ from Baseband GeneratorI from Baseband GeneratorSource BasicsCopyright 2000Digital Signal Generator Block DiagramBaseband GeneratorDACDACPattern RAMCo

34、nstellation Map and Baseband FiltersTimingDataData ClockSymbol ClockFrom CPUIQAnalog Reconstruction FiltersSource BasicsCopyright 2000Digital Signal GeneratorFormat Specific Digital SignalsNADC (TDMA IS-54) ParameterSpecificationAccess MethodTDMA/FDDModulationp/4 DQPSKChannel Bandwidth30 kHzReverse

35、Channel Frequency Band824 - 849 MHzForward Channel Frequency Band869 - 894 MHzFiltering0.35 RRCSource BasicsCopyright 2000Digital Signal GeneratorAccess and Framingone frame = 1944 bits (972 symbols) = 40ms; 25frames/sec slot 1 slot 2 slot 3 slot 4 slot 5 slot 6324 bit (162 symbols) = 6.667ms G R Da

36、ta Sync Data SACCH CDVCC Data 6 6 16 28 122 12 12 122Mobile to Base StationSource BasicsCopyright 2000Applications and Critical SpecificationsAnalog and DigitallReceiver Sensitivityfrequency accuracylevel accuracyerror vector magnitudelReceiver Selectivityphase noisespuriousspectral accuracylSpectra

37、l RegrowthACP performanceSource BasicsCopyright 2000Applications and Critical SpecificationsReceiver Sensitivity Want to measuresensitivity in a channelMeasurement impaired by frequency inaccuracyfrequency inaccuracyamplitude inaccuracyinput for signal generatorDUTlFrequency AccuracySource BasicsCop

38、yright 2000Applications and Critical SpecificationsReceiver Sensitivity Customer is testing a -110 dB sensitivity pager:Power Out -110 dB specificationCase 1: Source has +/-5 dB ofoutput power accuracy at-100 to -120 dBm output power.Set source to -115 dBmActual output power= -114 dBmXXX XXOCase 2: Source has +/-1 dB ofoutput power accuracy at-100 to -120 dBm output power.Power Out -110 dB specificationSet source to -111 dBmActual output power= -112 dBmXXO OOOX= Failed unitO=Pass