通原实验报告labview.docx

通原实验报告labview.docx

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通原实验报告labview

THECOMMUNICATIONFUNDAMENTALSEXPERIMENT

NAME:

单赟吉

STUDENTID：

11211105

CONTENTS

LEB2digitalcommunication3

1.ExperimentPrinciple3

2.ExperimentPurpose5

3.ExperimentalContent5

4.ExperimentalBlockDiagram6

PART1:

TheUARTcommunicationsystem7

PART2:

AnImageoveranLTIChannelandDealingwithNon-Ideality8

5.ExperimentalResults9

LEB5Altitudemodualtion11

1.ExperimentPrinciple11

2.ExperimentPurpose13

3.ExperimentalContent13

4.ExperimentalBlockDiagram14

PART1:

AMtransmitter14

PART2:

ASingle-/Multi-toneAMTransmitter14

PART3:

A*.wavAMtransmitter15

PART4:

AMreceiver16

5.ExperimentalResults17

LAB2

DIGTIALCOMMUNICATION

1.ExperimentPrinciple

1.1UARTprotocol

Asaforementioned,UARTiswidelyusedfordigitalchip-to-chipcommunicationsonembeddedsystems.Whiletherearemanyconfigurations,acommonUARTpacketstructureis10bits-1STARTbit,8DATAbits（onebyte）,and1STOPbit.Thisstructureisshowninfigure1below,andiscommonlyreferredtoas8n1（8databits,noparity,1stopbit）.Sometimesanadditionalbitisincludedforparitychecking（asimpleformoferrordetection）,butthatisnotcoveredinthislab.

ThedatabyteissentLSB（LeastSignificantBit）first,whichmeansweeffectively

sendthebyte"backwards."Forinstance,ifwewantedtosendthebyte00101001,we

wouldtransmitthefollowing10-bitsequence:

0100101001（onestartbit（0）,the8

databitsLSB->MSB（10010100）,andthenonestopbit

（1））.

Thesebitsareencodedasvoltages:

aHIGHvoltage（i.e.5volts）torepresenta1,

andaLOWvoltage（i.e.0volts）torepresenta0.TheSTARTbitisalwaysaLOW

state,andtheSTOPbitisalwaysaHIGHstate.Eachbitstateisheldforsome

periodoftime-thesymbolperiod-togeneratea’square-wave’typeofsignal.The

amountoftimeforwhichweholdaLOWorHIGHbitdeterminesthebaudrate

（speed）ofthelink.Inmostsystems,thetransmitterandreceiveragreeuponthis

baud（orbit-clock）rateinadvance.Theresultingpacketsignalissentalongawire

fromthetransmittertothereceiver.

UARTpacketscanbesentfromthetransmitteratanypointintime,andtherecan

beanyamountoftimeinbetweenpackets,hencetheasynchronousnatureofthis

communicationlink.Inordertoachievesynchronizationwithanincomingpacket,

thecommunicationwireidlesintheHIGH

（1）stateinbetweenpackets.Sincethe

STARTbitisalwaysaLOW,weknowapackethasbegunwhenthistransitionoccurs.

Afterwesynchronizetothestartofapacket,weusetheknownbaudratetoestimate

thecenterofeachdatabit,andsamplethevoltageofthesignalatthispoint.In

figure2below,weillustratethestartofapacketandthedata-bitsamplinginterval.

Afterthereceiverdecodestheentiredatapacket,wereversetheresult（togetthe

originalMSB->LSB）byte,andwe’redone!

We’vereceivedoneUARTpacket.The

stopbitsimplyreturnsthecommunicationswiretotheoriginalIDLE（HIGH）state,

andthereceiverbeginswaitingforthenextSTARTbitwhichsignalsthebeginning

ofthenextpacket.

1.2UARTdecoder

Thetransmitterencodes0’sas0Voltsand1’sas5Volts.EachcharacterofthemessageisrepresentedusingASCIIencoding.ASCIIisaone-byte（8bit）representationfor256ofthemostofthecommonlyusedcharactersintheEnglishlanguage.Asaresult,eachUARTpacketyouwillreceiveconsistsofasinglecharacterfromthismessage.Thecharactersofthemessagearesentinorder,sothey

shouldbekeptintheorderthattheyarereceived.Afterdecodingtheentirestream,

youwillhavereceivedaquestion.

1.3EstimatinganLTIchannel

Theadditional’byte’（arrayelement）whichispre-pendedtothepicturearray.Itcontainsdecimal85,whichisequivalenttobinary01010101.YourentirefirstUARTpacket,includingthestartandstopbit,willthenbe0101010101（rememberthedataordergoesLSB->MSB）.

We’llcallthispacketthesynchronization&trainingpacket.Thefollowingadditionalpiecesofinformation:

1.BeforethestartofthefirstUARTpacket,thetransmittersends’11111111’.

ThisissimplytoensurethatwebeginwiththecommunicationlineIDLEing

HIGH.

2.Followingthesefirsteight1’s,wesendtheaforementioned"synchronization"

packet.

3.TheLTIchannelimpulseresponseisnomorethan8tapslong（h[i]=08i>

7）,andthechannelisnoise-free.

4.Thefirsttapofthechannelimpulseisguaranteedtobenon-zero（h[0]6=0）

5.BeforetheUARTtransmissionstarts,thestateofthecommunicationlineis

unknown（x[i]unknown8i<0）

6.Afterthisfirstpacket,thecommunicationcontinuesasusual:

itsendsthepixels

oftheimage.

1.4Correctingforthechannel

Wewillconsiderasimpleexampletodemonstratehowyouaregoingto’correct’for

thechannel:

Considerthecasewhereyouhaveachannelwhichhasaresponseof

length2,andweknowthefirsttapisnon-zero.Theoutputy[n]atanygiventimeis

then

Now,let’sassumewesuccessfullybuiltachannelestimationblocktodetermineh[0]

andh[1].Let’salsoassumethatweknowx[n-1],sincethatwastheprevioussymbol

weshouldhavealreadydecoded（thinkaboutthisforamoment-it’sarecursive

argument）.Sinceweknoweverythingbesidesx[n],wejustre-arrangetheabove

equationtogetanestimateofthecurrentsample:

2.ExperimentPurpose

InLab2,ourgoalistoknowsomeaspectsofdigitalsignaling,includingsimplechannelcodesandtheeffectofsendingthesesignalsovernon-idealcommunicationchannels.

3.ExperimentalContent

3.1Part1:

TheUARTcommunicationsystem

Inthislab,themainmissionisthedecoder.Wecanputitinto3steps.Step1:

BuildtheReceiverStateMachine.Step2:

Decodetheincomingsamplestream.Step3:

Readthequestion!

3.2Part2:

AnImageoveranLTIChannel,andDealingwithNon-Ideality

Thegoalforthispartofthelabistoknowsomethingaboutnon-idealchannelsandthetheoryofdeconvolution.First,Verifythatyourreceiverstillworks.ThenEstimatinganLTIchannel.Finally,Correctingforthechannel.

4.ExperimentalBlockDiagram

PART1:

TheUARTcommunicationsystem

a.Thewholeblockdiagram

TheASCIItransmitterandtheconverterhavealreadyfinished,thusweonlybuildtheUARTreceiversystemtocompletethecommunicationsystem.

b.theUARTreceiver

Thediagramgivenistoosimple,Imustdoalotofworktofinishit.ButthereisthesamereceiverintheLab2whichhasfinished.SoIjustlinkeverymodules.Finally,thewholesystemofthereceiverisasblow.Iwillshowyouhowitworksinthefollowingpaper.

c.Decisionregeneration

Beforeintothestatemachine,thesignalmustbeidentifiedashighelectricallevelorlow.Weneedadecisionregenerationmoduletochoosethestateofthecode.

d.Theadditionof1Darray

IntheREADstatewemustaddthearrayafterdecimating

e.TheRegister

Wealsoneedaregistertosavethedataafterthedecodingandoutputallatlasttogettheresult

f.TheIDLEstate

ThislinkformiswaitingtoseeatransitionfromHIGH->LOW.Ontransition,

gotostateREAD.

PART2:

AnImageoveranLTIChannel,andDealingwithNon-Ideality

TheUARTreceiverhasalreadybuiltup,themissionistocompletethechannelcorrection.

Thewholeblockdiagramofthechannelcorrectionisshownasthisfigure.

5.ExperimentalResults

PART1:

thereceivercanreceivethecode“Howareyou?

”byrecoveringtheASCIIformthetransmitter.

LAB5

AmplitudeModulation

1.ExperimentPrinciple

1．1AmplitudeModulation

AmplitudeModulation（AM）isananalogmodulationschemewheretheamplitude（A）ofafixed-frequencycarriersignaliscontinuouslymodifiedtorepresentdatainamessage.Thecarriersignalisgenerallyahighfrequencysinewaveusedto“carry”theinformationontheenvelopeofthemessage.Theresultisadouble-sidebandsignal,centeredonthecarrierfrequency,withtwicethebandwidthoftheoriginalsignal.Themathematicalexpressionofmodulatedwaveis:

Here,A0representsDCcomponentofthemodulationsignalm（t）,f（t）representsACcomponentofthemodulationsignal,thecarrierwaveweusehasunitamplitude,angularfrequencyisafixedvaluewc,theinitialphaseofthecarriersignalc（t）isθ0.

From（1.1）,wecanconcludethatAmplitudeModulationistheproductofmodulationsignalm（t）andcarriersignalc（t）.Inordertorealizethattheamplitudeofcarriersignalcoordinatedbyf（t）linearly,m（t）shouldconsistofDCcomponenttomakesurem（t）≥0,i.e.,

Therefore,theenvelopofSam（t）iscompletelyabovetimeaxis,asshowninfigure1.

Figure.1TimedomainofanAMsignal

For

wecanobtainitsspectrumby

FouriertransformdirectlyasshowninFigure.2:

TherearethreefundamentalAMmethodsknownasDSB（DoubleSide-Band）,SSB（SingleSide-Band）,VSB（VestigialSide-Band）.

1.2AmplitudeDemodulation

Sincethecoreideaofthesoftwareradioistrytoattachtheanalog-to-digitalconvertertoanantennaandgetthesoftwareasclosetotheantennaasfeasible,theprocessofvariousmodulationanddemodulationtowardsthesourcesignaliscarriedoutindigitaldomain.

PCterminalsendsasourcesignaltothegeneralsoftwareradioplatformUSRP-2920viagigabitEthernetinterface,andthenusetwohighspeedD/Aconvertertoupconvertsourcesignal,finallymanipulatetheorthogonalizationI/Qmodulationafterlowpassfiltering.Amongthem,theI/Qrepresentsthein-phasecomponent（I）andquadraturecomponent（Q）,andtheresultingI/QsamplingpointsafterpaeventuallysenttothetransmittingantennaagigabitEthernetinterfaceissenttothePC,thewholeprocessofsignalprocessinginLabVIEW

For