PSpice for Analog Communications Engineering

154 Pages·2007·23.69 MB·English

MOBK065-FM MOBKXXX-Sample.cls March22,2007 13:41
PSpice for Analog
Communications Engineering
MOBK065-FM MOBKXXX-Sample.cls March22,2007 13:41
Copyright© 2007byMorgan&Claypool
Allrightsreserved.Nopartofthispublicationmaybereproduced,storedinaretrievalsystem,ortransmittedin
anyformorbyanymeans—electronic,mechanical,photocopy,recording,oranyotherexceptforbriefquotations
inprintedreviews,withoutthepriorpermissionofthepublisher.
PSpiceforAnalogCommunicationsEngineering
PaulTobin
www.morganclaypool.com
ISBN:1598291602 paperback
ISBN:9781598291605 paperback
ISBN:1598291610 ebook
ISBN:9781598291612 ebook
DOI10.2200/S00071ED1V01Y200612DCS009
APublicationintheMorgan&ClaypoolPublishersseries
SYNTHESISLECTURESONDIGITALCIRCUITSANDSYSTEMS#9
Lecture#9
SeriesEditor:MitchellA.Thornton,SouthernMethodistUniversity
LibraryofCongressCataloging-in-PublicationData
SeriesISSN: 1932-3166 print
SeriesISSN: 1932-3174 electronic
FirstEdition
10987654321
MOBK065-FM MOBKXXX-Sample.cls March22,2007 13:41
PSpice for Analog
Communications Engineering
PaulTobin
SchoolofElectronicandCommunicationsEngineering
DublinInstituteofTechnology
Ireland
SYNTHESISLECTURESONDIGITALCIRCUITSANDSYSTEMS#9
M
&C &
M o r g a n C l a y p o o l P u b l i s h e r s
iv
ABSTRACT
In PSpice for Analog Communications Engineering we simulate the difficult principles of ana-
log modulation using the superb free simulation software Cadence Orcad PSpice V10.5.While
use is made of analog behavioral model parts (ABM),we use actual circuitry in most of the sim-
ulation circuits.For example,we use the 4-quadrant multiplier IC AD633 as a modulator and
import real speech as the modulating source and look at the trapezoidal method for measuring
the modulation index.Modulation is the process of relocating signals to different parts of the
radio frequency spectrum by modifying certain parameters of the carrier in accordance with the
modulating/information signals.In amplitude modulation,the modulating source changes the
carrier amplitude,but in frequency modulation it causes the carrier frequency to change (and in
phase modulation it’s the carrier phase).
The digital equivalent of these modulation techniques are examined in PSpice for Digital
Communications Engineering,where we look at QAM,FSK,PSK and variants.We examine a
range of oscillators and plot Nyquist diagrams showing the marginal stability of these systems.
The superhetrodyne principle, the backbone of modern receivers is simulated using discrete
components followed by simulating complete AM and FM receivers.In this exercise we exam-
ine the problems of matching individual stages and the use of double-tuned RF circuits to
accommodate the large FM signal bandwidth.
KEYWORDS
Amplitude modulation,frequency modulation,phase modulation,radio-frequency amplifiers,
superhetrodyne receivers,phase lock loops,Nyquist plot,gain and phase margins.
MOBK065-FM MOBKXXX-Sample.cls March22,2007 13:41
I dedicate this book to my wife and friend, Marie and
sons Lee, Roy, Scott and Keith and my parents
(Eddie and Roseanne), sisters, Sylvia,
Madeleine, Jean, and brother, Ted.
MOBK065-FM MOBKXXX-Sample.cls March22,2007 13:41
MOBK065-FM MOBKXXX-Sample.cls March22,2007 13:41
vii
Contents
1. AmplitudeModulationTechniques.............................................1
1.1 BasebandtoPassband .................................................... 1
1.2 TheCommunicationsChannel............................................1
1.2.1 AmplitudeModulation............................................2
1.2.2 AMGeneration:Method1........................................3
1.2.3 AMusingAnalogBehavioralModels:Method2.....................4
1.2.4 AMGeneration:Method3........................................5
1.3 PowerinanAMSignal...................................................6
1.3.1 TransmissionEfficiency...........................................7
1.4 TrapezoidalMethod:Speech-ModulatedDSBFCAMSignal................7
1.5 SpectrumofSpeech-ModulatedAMSignal.................................9
1.6 TheFour-QuadrantAD633MultiplierIC..................................9
1.7 LinearAmplitudeModulator..............................................9
1.7.1 Multiplying,Squaring,andFrequencyDoubling....................12
1.8 Exercises...............................................................15
2. AMDiodeDetectionandFour-QuadrantMultipliers..........................19
2.1 AMDetection..........................................................19
2.1.1 PrecisionRectifier ............................................... 19
2.1.2 DiagonalClippingDistortion.....................................19
2.1.3 ChoiceofTimeConstant.........................................21
2.2 AutomaticGainControl.................................................23
2.2.1 ProbeLogCommand............................................24
2.3 Double-SidebandSuppressedCarrier ..................................... 25
2.3.1 Double-BalancedModulator......................................26
2.3.2 CoherentDetection..............................................26
2.4 DSBSCProductionusingFour-QuadrantMultipliers......................28
2.4.1 DSBSCDemodulation...........................................28
2.5 Exercises...............................................................29
3. SystemStability,NyquistCriterion............................................33
3.1 NyquistCriterion.......................................................33
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viii PSPICEFORANALOGCOMMUNICATIONSENGINEERING
3.2 JFETColpittsOscillator.................................................33
3.2.1 TheFeedbackNetwork .......................................... 35
3.2.2 Closed-LoopTesting ............................................ 37
3.2.3 TheOutputFile.................................................38
3.2.4 TheOscillatorOutput ........................................... 38
3.3 HartleyOscillator.......................................................38
3.4 QuartzCrystalandEquivalentCircuits....................................41
3.4.1 QuartzCrystalResponse ......................................... 41
3.4.2 CMOSColpittsCrystalOscillator ................................ 41
3.5 Phase-ShiftOscillator...................................................43
3.5.1 GainandPhaseMargins ......................................... 44
3.5.2 NyquistPlot.....................................................44
3.5.3 NyquistDiagramandOscillators..................................45
3.6 Exercises...............................................................46
4. SuperhetrodyneAmplitudeModulationReceivers..............................51
4.1 NonlinearMixing.......................................................51
4.2 JFETNonlinearMixerCircuit...........................................52
4.2.1 MixerOutput...................................................52
4.2.2 Superhetrodyning................................................53
4.2.3 ImageFrequency ................................................ 53
4.2.4 SuperhetrodyningandImageFrequencies..........................56
4.3 AMSuperhetrodyneReceiver............................................56
4.3.1 TheInput/MixerStage...........................................57
4.3.2 TheLocalOscillator:ArithmeticSelectivity........................58
4.3.3 JFET-TunedRadioFrequencyAmplifier..........................60
4.3.4 RF-TunedAmplifierMeasurements...............................60
4.4 MeasuringtheOutputImpedanceofanRFAmplifier......................62
4.4.1 ACEquivalentCircuit...........................................64
4.5 BJTBandpassAmplifier.................................................65
4.5.1 TuningCapacitance..............................................66
4.6 DiodeDetectionandAutomaticGainControl.............................67
4.7 PowerAmplifierStage...................................................67
4.8 AudioOutputSignals ................................................... 67
4.9 RFSignals..............................................................69
4.10 SpeechScrambling......................................................69
4.11 Exercises...............................................................70
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CONTENTS ix
5. FrequencyModulationPrinciples.............................................75
5.1 ModulationIndex.......................................................75
5.2 FMSpectrum...........................................................76
5.3 FMProductionusingtheVSFFMGeneratorPart..........................77
5.3.1 PowerinanFMSignal...........................................78
5.4 VaractorDiode ......................................................... 79
5.4.1 FMOscilloscopeDisplay.........................................81
5.4.2 FMPreemphasisandDeemphasis.................................81
5.5 FMStereoGeneration...................................................83
5.5.1 FMBasebandStereoSignals......................................84
5.6 ReplacingABMPartswithCircuitry......................................86
5.7 FMStereoReception....................................................87
5.8 Exercises...............................................................88
6. SuperhetrodyneFrequencyModulationReceivers..............................95
6.1 FMSuperhetrodyneReceiver.............................................95
6.1.1 MixerStage.....................................................96
6.2 Coupled-TunedRFAmplifiers...........................................97
6.2.1 Double-TunedIntermediateRFAmplifier.........................99
6.3 AutomaticGainControl................................................100
6.4 ThePhase-LockLoopDetector.........................................101
6.4.1 PLLCompensation.............................................103
6.4.2 TheLockandCaptureRange....................................105
6.4.3 ABMPhase-LockedLoop ...................................... 105
6.5 FrequencyDemodulation...............................................106
6.5.1 ReceiverWaveforms............................................109
6.6 Exercises..............................................................109
7. Noise.......................................................................115
7.1 SourcesofNoise.......................................................115
7.2 NoiseFactorandNoiseFigure..........................................116
7.3 Defriis’Formula ....................................................... 116
7.3.1 CommonEmitterAmplifier.....................................117
7.4 TheOutputFile.......................................................117
7.5 ProbeExpressionCommands...........................................118
7.6 The“(if,then,else)”Command ......................................... 118
7.7 ImportingNoise.......................................................121
7.7.1 AddingNoisetotheInputSignal................................121
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x PSPICEFORANALOGCOMMUNICATIONSENGINEERING
7.8 Exercises..............................................................122
AppendixA...........................................................129
References.............................................................133
Index.......................................................................135
AuthorBiography...........................................................139