SDRSOFTWAREDEFINEDRADIO

NARCPRESENTATION– JANUARY2016

STEPHENOLESEN – VE6SLP

WHATISSDR?

• SDR– SoftwareDefinedRadio

• InsteadofusingdiscretecomponentsordedicatedICsfortuning, receptionanddemodulation,softwaremaytakeonmanyoftheseroles.

• Hardwarecomponent tendstoonlyprovideRFtoIFconversion (including azero-IF).

• Usessoftwaretodemodulatereceivedsignals.

• Usessoftwaretomodulatetransmittedsignals.

WHYUSESDR?

• SDRprovides flexibilitybyremoving restrictionsimposedbyhardwareinthesignalchain.

• AsingleRFfrontendcanbeusedbymultiple signalprocessorsastheincomingRFisdigitizedearlyon intheprocess.

• Generalpurposecomputerscanbeusedwithhighperformance toanalyzeandworkwithcomplexsignalsormultiple (independent ordependent) signalsatonce.

• DigitizationoftheRFsignalinbothdirectionsallowsforveryaccuratereproduction andanalysisofsignalswithout introducing further noiseinanalogcomponents.

BASICCONCEPTSHARDWARECOMPONENTS

• Thehardwareinvolves:

• AnRFfrontend,generallycanbequitewidebandandoftenfoundasamonolithicIC.

• Analogtodigitalconversion,eitherfromanIForfrombaseband.

• Inatransmitter,adigitaltoanalogconverterisalsoused.

• Maysendbaseband toanIFmixerordirecttoRF.

• ComponentsaresimpleraslessamplificationneedstotakeplacebeforetheADC,filtering andprocessingaredonedigitallyinsoftware.

BASICCONCEPTSSOFTWARECOMPONENTS

• ThesoftwareonlyneedstoworkwithadigitalstreamofdatawhichistheRFdataconvertedfromtheRFfrontend.

• Softwarecanreceiverealsamplesorcomplexsamples(I/Q– in-phase/quadrature).

• Canrunasaservice,asauserapplication, indedicatedhardware(suchasFPGAs,DSPsorevenArduinos/microcontrollers).

• Datacanbetransmitteddigitallyovernetworkswithout lossof signalfidelity.

BASICCONCEPTSSOFTWARE

• Examplesofsoftwareinclude:

• SDR#(SDRSharp,Windows)

• SDR-Console(Windows)

• HDSDR(Windows)

• GNURadio(Linux)

• Linrad (Linux)

• SDR-Shell(Linux)

• Gqrx (Linux,Mac)

• WebSDR (Linux,provideswebinterfacetomultipleusers)

BASICCONCEPTSRFDIGITIZATION

• TheRFisreceivedonanantenna.

• RFfrontendusuallyprovidesnormal frontend filtering (bandpass, lowpass,etc.)

• RFiseitherdirectlymixedtobasebandortoanIF

• IFiseitherdirectlysampledormixedtobaseband

• Samplesaresenttothecomputeraseitherrealorcomplexsamples

• Realcanbeconvertedtocomplex,andviceversa

• Basebandcaneasilybesampledwithacomputersoundcard

• IFgenerallyrequiresdedicatedhardwarefortheconversionofthehigh frequency IF

• Receivebandwidth limitedbytheanalogtodigitalconverter(orsound card)

BASICCONCEPTSDEALINGWITHTHEDIGITALSIGNAL

• TherealsamplesgenerallyareconvertedtoI/Qsamples,providing a90degreeoutofphasesampleoftheRFdata

• Thecomplexsampleisabletoproduceamplitudeandphaseacrosstheentirereceivedspectrumwhileeliminating imagesduetomixing

• Realsampleswhenconvertedhavenodirectphaseinformation andwillhaveanimagesignalpresentafterconversion• Thiscanberemovedusingdigitalfilters

• Digitalsignalcanbesentthrough extremelycomplexormany-poledfiltersprovidingsharp,narrowfiltersontherawRFdata

• Originalsignaldatacanbeusedinmultiple filters/demodulators simultaneouslyacrosstheentirereceivedbandwidth.

BASICCONCEPTSSAMPLINGRATE,NUMBEROFBITS,BANDWIDTH

• SincetheRFsignalisdigitized, theanalogtodigitalconversionwillhaveafixedsamplerate.

• Depending onthehardware(ADCandDAC),thissampling ratemaybeatsoundcardspeeds(48or96kHz,or96kSPS/192kSPS) orhigher (suchastheBladeRF at40MSPS)

• Usablebandwidth ishalfthesampling rate(192kSPSprovides96kHzbandwidth,40MSPSprovides20MHzbandwidth)

• Bitlengthprovides thetotalsignalamplitude rangeandrelatesstronglytotheachievableSNR,dynamicrange,accuracyandoverloadcharacteristics.8bitsiscommon,providing 256levelsofsignalstrength.

COMMONHARDWARERTL-SDR

• SimpleUSBdevicesknownasRTL-SDR(RTL2832)areeasytofindandalowcostwaytoexperiment withreceptiononlySDR.

• AvailableinCanadaforaslowas$15,butgenerally intherangeof$25-$30.

• Availablewithavarietyoftunerchipsets,mostcommonthesedaysistheR820T.

• ConnectsviaUSBtoacomputer.

• Abletotunefromaround50MHzto1.5GHzandabove.

• Provides8bitsamplesatupto3.2MSPS(usuallyonlyusableupto2.4MSPSorso)

COMMONHARDWARESOFTROCK

• TheSoftrock seriesbyFiveDash(KB9YIG)areakitversionofHFSDRswhichuseacomputersoundcardforthedigitizationportion.

• LowcostandasimpledesignallowagoodunderstandingofthehardwaresideofSDR.

• Rangeinpricefrom$21USDtoaround$100USD.

• UseUSBforpowerandfrequencycontrol,regular3.5mmaudiocablesforthebasebandaudiotobedigitized.

• Compatiblewithawidevarietyofsoftwareastheonlyrequirementisthesoundcarddriver.

• Capableofbothtransmission(lowpower,around1watt)andreception,96kHzbandwidth(192kSPS)

COMMONHARDWAREFLEXSDR

• FlexRadioprovidesall-in-onesolutions forhighendperformance.

• Acombinationofhardwarebaseddigitalprocessingandcomputerbasedsignalprocessing.

• Higherpoweroutputs thantheSoftRock.

• Rangeinpricefrom$1000to$11,000.

• Familiarriglayoutanddesignwithmanyinputandoutputoptions.

• NARCownsaFlexRadioSDRattheshack.

• Somesupport dualRFfrontends,widebandwidth (not limitedbyacomputersoundcard)

ADVANCEDHARDWAREBLADERF ANDHACKRF• BoththeBladeRF andHackRF aresmallUSBcontrolledSDRhardwarefrontends.

• ProvideonboardADCandDAC.• BladeRF capableoffullduplexcommunication.

• Verylowoutputpowers(10mWorless).

• BladeRF iscapableof40MSPSand300MHzto3.8GHztransmit/receive,12bits.

• HackRF iscapableof20MSPSand1Mhzto6GHz,8bits.

• BladeRF runsaround$600-$1000USD,HackRF isaround$350-450USD.

• BladeRF hasanonboardFPGA,HackRF usesaCPLD.

• Designedforexperimentation,protocoldesign,advanceddecoding.

• TheyhavebeenusedtoprovideGSM/LTEcellularnetworkservices,digitalTV(ATSC)transmission,andmore.

USINGWHATYOUHAVEANYRIGUSINGASOUNDCARD

• SincetherealideaofSDRisthatsoftwarehandlesallthesignalprocessing,anyRFfrontend cantheoreticallybeusedtogetthesignalintothesoftware.

• Usinganormalradio(HF,VHF,UHF,etc.)withanaudioconnection toacomputercanprovide low-bandwidthSDRservices.

• Bandwidth limitedbythein-radiofilters(USB,LSB,FM,etc.)

• Thissortof setupiscommonly foundwithPSK,JT65,WSPR.

• TheRFfrontend isafullradiocapableofdemodulation ofaudio,butisunawareofwhatthataudio is.Thecomputer thenprocessestheinput likeanSDRtoprovide thesedigitalmodes.

• Fldigi andHamRadioDeluxeprovideconvenient interfacestoclassicradiosviathesoundcard(andoftenaconnecting interfacetoprovidePTTandlevelcontrol).

INTERFACINGUSBANDSOUNDCARDINPUTS

• ThesimplestSDRRFfrontendoutputs thebasebandsignalviaregularanalogaudiosignalstoacomputer’s soundcard.

• Limitedbandwidth (audiobandwidthranges).

• I/Qimbalanceismorecommonandhardertofix.

• USBinputsvary,withdevicesliketheRTL-SDR,Flex,BladeRF andHackRF havingintegratedADCs/DACs.

• SomeUSBSDRdevicesusebuilt-insoundcardswhichconnectoverUSB,butarestilllimitedtoaudioranges.TheRigBlaster seriesisanexampleofanSDR-likeinterfacewithintegratedsoundcard.

COSTOVERVIEW

• Startingwithequipmentyoualreadyhave,experiencing thebasicsofSDRandtheintegrationofcomputerswithradios,cancostnearlynothing.

• UsinganRTL-SDRbasedUSBadaptercangetyouupandrunning forunder$25.

• Adding ontransmitcapabilitiescanstartaslowas$70fortheSoftRock,uptotheFlexRadioseriesatmanythousand ofdollars.

• BecausetheRFportion isrelativelystraightforward,designing yourownSDRfrontend canbedone(thisgenerallyinvolvesoversamplingyourdesired frequency togetI/QsamplesandmixingwithanIFtoconverttobaseband,andnotmuchelse).

RFCHARACTERISTICS

• Ingeneral,SDRprovides foracleanoutput signal.

• Sharpandcomplexfilterscanbeusedinsoftwaretoremoveasmuchextrasideband/noise aspossible.

• ExtremelycomplexsignalscanbesentdigitallytoahighperformanceDACwhichproduces thevoltageoutput totheRFtransmitterwithoutneeding complexanalogfiltersorintegrationtojoinmultiplesignalstogether.

• Signalnoise isinfluencedbythebitsizeandsamplerateusedtogeneratethesignal.

• SincetheRFfrontend isstraightforward(ADC/DAC,mixerandamplifier), thesignalpathisshort,preventingextraoscillatorsandparasitics fromcompromising thesignal.

SOMEEXAMPLEUSES

• ADS-B(1090MHz)planetransponder tracking

• Multi-channel trunking scanners

• Widebandbandlistening/waterfall(includingmulti-userdemodulation), ie.WebSDR

• Remotelistening/transmitting

• PSK, JT65,WSPR(allatthesametime,withoneantennaandSDRfrontend)

• Experimentaldigitaloranalogmodedesign

• Satellitetrackingandtelemetry

• Discovering theRFworldaroundyouwithout spinning thedial(awidebandwidth receivershowing20MHzofRFspectrumatoncegivesaniceoverviewofnearlyalltheHFspectrumatonce)

QUESTIONS?

• Orfeelfreetosendmequestionsatve6slp@narc.net