aps专业课英文总结 通信原理.docx
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aps专业课英文总结 通信原理.docx
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aps专业课英文总结通信原理
Chapter1introduction
1.ThefunctionoftheCommunicationsystemissendingtheinformationfromtheonesourcetooneormoredestinations.
2.Generalmodelofcommunicationsystem:
Source---transmitter---communicationchannel---receiver---destination(sink)
|
Noise
Source:
toconvertthevariousmessagesintotheoriginalelectricsignals
Transmitter:
togeneratesignalswhicharesuitablefortransmissionchannels.
Communicationchannel:
aphysicalmedium,totransmitsignalsfromthetransmittertothereceiver.
Receiver:
toamplifysignalanddosomeinversetransform,andrecovertheoriginalsignalsfromthederogativereceivedsignals.
Sink:
restoreelectricalsignalsintomessages
3.Classificationofsignals
Analogsignals:
thevalueofelectricalparametersarecontinuous
Digitalsignals:
thenumberofelectricalparametersisfinite
4.Modelofanalogcommunicationsystem
Source---modulator---communicationchannel---demodulator---receiver
|
Noise
5.Digitalcommunicationsystem:
Source---sourceencoding---channelencoding---digitalmodulation---communicationchannel----digitaldemodulation---channeldecoding---sourcedecoding---receiver
Sourceencodinganddecoding:
(1)improvetheeffectivenessofthetransmissionofinformation
(2)completeA/D
Channelencodinganddecoding:
enhancedanti-interferencecapabilityofthedigitalsignals.(obeysomerulestoputsomesymbol)
Digitalmodulationanddemodulation:
digitalmodulationistomovethefrequencyspectrumofthedigitalbasebandsignaltothehigherfrequencies,makethesignalssuitablefortransmissionchannels.Demodulationistorestorethedigitalbasebandsignals.
6.Theadvantagesofdigitalsignals:
(1)Stronganti-interferenceability
(2)Controllabletransmissionerrors
(3)Easyintegration
(4)Easyencryption
7.Communicationmode:
Simplexcommunication
Half-duplexcommunication
Full-duplexcommunication
Chapter4channel
1.Wirelesschannel:
usingelectromagneticwavepropagationinspacetotransmitsignals.
Classification:
groundwave(lowerthan2MHz);skywave(2MHz---30MHz,usingionosphere);lineofsight(higherthan30MHz,usingradiorelay)
2.Wiredchannel:
usingartificialelectricalconductivityoropticalsignaltransmissionmediumtotransmitsignals.
Classification:
openwire(parallelwireerectedontheelectricalpoles);
symmetricalcable(twistwire);
coaxialcable(TVbroadcasting);
opticalfiber
3.Mathematicalmodelofchannel:
Modulationchannelmodel:
isalwaysthere,thusitisnamedadditivenoise
Thisisgeneralmathematicalmodel,k(t)isaverycomplexfunction,reflectingthechannelcharacteristics
K(t)isseenasmultiplicativeinterference,K(t)changesovertimecalledrandomchannel,onthecontrary,calledconstantchannel.
Codingchannel:
characteristicsdescriptedtransferprobability,whichmeanserrorsinsequenceofnumber
Chapter5analogmodulationsystem
1.Modulation:
basebandmodulationandcarriermodulation
carriermodulation:
usingmodulatedsignaltocontrolparametersofcarriersignals,modulatedsignalisthebasebandsignal.
2.AM:
Timedomainexpression:
Modelis
AMsignalsfrequencyspectrum:
envelopeissameasm(t)
3.DSB:
Frequencyexpression:
Thereisnocarriercomponent,thusmodulationefficiencyis100%,butthebandwidthisthesameasAM,B=2
4.SSB:
Timedomainexpression:
^meansHilbertTransform,
Filtermethod:
getUSB
Or
getLSB
Phase-shiftmethod:
makeappropriatephaseshiftofcarrierandmodulatedsignals,sothattherewillbeasidebandeliminatedbycombiningcarrierandmodulatedsignals
5.VSB:
6.Coherentdemodulation:
Envelopedetector(noncoherent)
TheamplitudeishigherthanVD,thecapacitorischarged,lowerthanVD,isdischarged.
7.Phasemodulation(PM):
isphasemodulationsensitivity(rad/V),
8.Frequencymodulation(FM):
isFMsensitivity(rad/s*V),
9.M(t)firstdodifferentialtransformationthendoFM,wecangetPM,onthecontrary,M(t)firstdointegraltransformationthendoPM,wecangetFM.
10.Non-coherentdemodulation(FM):
First,throughthedifferentialcircuit:
Thenthroughtheenvelopedetector
11.coherentdemodulation(FM):
itisjustsuitableforNBFM.
Chapter6digitalbasebandtransmissionsystem
1.Digitalbasebandsignalwaveform:
(a)Unipolarwaveform
(b)Bipolarwaveform
(c)Returntozerounipolarwaveform
(d)Returntozerobipolarwaveform
(e)Differentialwaveform
(f)Multi-levelwaveform
2.Transmissioncode
AMI(alternativemarkinversion):
Advantages:
noDCcomponent,lowandhighfrequencycomponent
Disadvantage:
itisdifficulttogettimingsignalswhentheleveldonotchangeforalongtime
(
orderhighdensitybipolar)
Manchester
0as01,1as10
Advantages:
noDCcomponent,richtiminginformation
Disadvantage:
doublingthebandwidth
CMI(codedmarkinversion)
1changeas‘11’and‘00’,0as‘01’
Sothatthe‘10’canbeusedaserrordetection.抽样判决器
3.Digitalbasebandtransmissionsystem
Sendingfilter:
generatedigitalbasebandsignalswhicharesuitabletotransmitinchannel.
Receivingfilter:
toreceivesignalsandfilteroutnoiseandotherinterference.
Samplingdecider:
restorebasebandsignals,baseontimingpulse.
Interference:
(1)Addictivenoise
(2)InterSymbolinterference(generatedistortion)
4.Eyemap
Samplingdistortion
Zerocrossingpointdistortion
Judgingthresholdlevel
Timingerrorsensitivity
Noisemargin
Chapter7digitalbandpasstransmission
1.Digitalmodulation:
2ASK(binaryamplitudeshiftkeying):
Onoffkeying(OOK)
Modulator:
(1)
(2)
Demodulator:
(1)Noncoherent:
(2)coherent
2FSK(binaryfrequencyshiftkeying):
Modulator:
Demodulator:
2PSK(binaryphaseshiftkeying):
Thusequalto
Modulator:
Demodulator:
2DPSK(binarydifferentialphaseshiftkeying):
Modulator:
firstchangetodifferentialsignals
Demodulator:
(1)
(2)
Chapter9analogsignalsthroughdigitaltransmission
1.threestep:
sampling---quantization---coding
2.low-passanalogsignalssamplingtheorem
3.band-passanalogsignalssamplingtheorem
4.PAM(pulseamplitudemodulation):
5.Quantization:
NbinarycodecanrepresentM=
samplevalues
Andbecausetheoutputlevelarenotequaltosamplevalues,sotherewillbeerrors,calledquantizationnoise
Uniformquantization:
Becausenumberoflevelandquantizedintervalofquantizerisdecided,sothequantizationnoiseisdecided,thusforsmall-signal,thesignal-to-noiseratioisnotideal.
6.nonuniformquantization:
improvethesignal-to-noiseratioofsmall-signal
inputvoltagextransformtooutputvoltagey
7.coding:
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