RFMicrowave Low Noise Oscillators.docx

RFMicrowave Low Noise Oscillators.docx

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RFMicrowaveLowNoiseOscillators

RF/MicrowaveLowNoiseOscillators

LiangZhou,YimingYou,MarcSalin,C.Broomfield,JKAEverard

Theorieshavebeendevelopedwhichshowhowminimumsidebandnoisecanbeobtainedinoscillators.Itisshownthatthereareanumberof optimumcouplingcoefficientsbetweentheresonatorandamplifierasillustratedinthefigurebelow.TypicallytheoptimumnoiseperformanceoccurswhenQL/Q0is1/2or2/3dependentonthedefinitionofpowerwithintheoscillator.InGeneralQL/Q0 =1/2isoptimum. Lownoiseoscillatorsoperatingfrom1MHzto10GHzhavebeenbuiltwhichuseInductorCapacitor（LC）,crystal,SurfaceAcousticWave（SAW）,Dielectric,HelicalandTransmissionLineResonators.Theseoscillatorsdemonstratenoiseperformanceusuallywithin1dBofthepredictedminimum.MMIClownoiseoscillatorshavebeendesignedandfabricated.Tunablelownoiseoscillators（bothhybridandMMIC）havebeenbuiltandareunderfurtherinvestigation.Nonlinearmodellingtechniques,usingVolterraSeries,havebeendevelopedwhichaccuratelypredicttheoutputpowerandtheoperatingfrequency.Ultra-lownoisereferencestandardsforoperationupto20GHzarebeingdevelopedusingsapphiredielectricresonators.Presentperformanceat7.5GHzexceeds-143dBc/Hz@10kHzoffset.Improvementsofaround35dBarecurrentlyunderinvestigation.Newtechniqueshavejustbeendeveloped（Sept.2000seepublications,patentapplicationsandbookbelow）whichsuppresstheflickernoiseby20dBdowntothethermallimitsforoffsetsabove10kHz. Thephasenoiseresultsarenowwithin1/2dBofthetheoreticalminimumnoiseperformancesetbythermalnoise. Thisisachievedbyusingfeedforwardamplifiersastheoscillatorsustainingstageandincorporatingthelimitingelsewhere.

SupportedbyEPSRC

Phasenoiseinoscillators:

NoisepowerversusQL/QOfromtheory（solidcurve）andexperiment（pointsx）.

FlickerNoiseMeasurementandReduction

JKAEverard,PDallas

FlickernoisecausesconsiderabledegradationtotheperformanceofoscillatorsanddividerswhichuseGaAs.AsystemformeasuringthelowfrequencyFlickernoiseonthegateanddrainofaGaAsFETandtheAMandPMcomponentsthattheseFlickernoisestransposeontoacarrierhasbeendevelopedasshownbelow.Thissystemhasbeenusedtomeasurethecrosscorrelationbetweenthelowfrequencyandthedemodulatedhighfrequencynoisesbymeasuringallthecomponentssimultaneouslyonadigitizingoscilloscope.ThesemeasurementscanbeusedtodeterminetheFlickernoisesourcesinGaAsFETsandthecorrelationbetweenthem.FlickernoisereductiontechniquesinGaAsFEToscillatorsarebeinginvestigated.TransposedGainOscillatorsoffer-143dBc/Hz@10kHzoffsetat7.5GHz.Newtechniqueshavejustbeendeveloped（Sept.2000seepublications,patentapplicationsandbookbelow）whichsuppresstheflickernoiseby20dBdowntothethermallimitsforoffsetsabove10kHz. Thephasenoiseresultsarenowwithin1/2dBofthetheoreticalminimumnoiseperformancesetbythermalnoise. Thisisachievedbyusingfeedforwardamplifiersastheoscillatorsustainingstageandincorporatingthelimitingelsewhere.Lowfrequencyfeedbackforflickernoisesuppressionisnowbeingre-investigatedandoptimised.

SupportedbyEPSRC

Noisemeasurementsystem.TypicalcrosscorrelationbetweendrainnoiseandAMcomponent

TunableResonatorsandLowLossFilters

JKAEverard

Newdesigntechniqueshavebeenappliedtomicrowavebandpassfilterstodemonstratecompactlowcostfiltersusingtransmissionlines,helicalresonatorsandcapacitors.Striplinefilterstructureswhichdemonstrateverylowradiationlosshavebeendevelopedasshown.ThesefiltersdonotrequirescreeningboxesandhavetheinherenthighQsofthematerialsused.UnloadedQsof520havebeenobtainedat5GHzinunscreenedfilters.Newresonators（bothhybridandMMIC）whichcantuneoveranearoctavefrequencyrangehavebeendevelopedforuseintunablemicrowaveoscillatorsandfilters.NewhighQ（235at2GHz）verycompactresonatorsandfiltershavebeendeveloped.

UltrahighQresonatorsoperatingatroomtemperaturearecurrentlyunderinvestigation.RoomtemperatureQsof24,000and60,000arereadilyachievedwithsimplestructuresusingBaTiO3andSapphirerespectively. Newstructureswitha10foldimprovementinQ（atroomtemperature）arecurrentlybeingmodelledandinvestigated.

SupportedbyEPSRC

Lowloss4.5GHzbandpassfilter.

Frequencyresponse（insertionloss）ofunscreenedbandpassfilter.

BroadbandPowerEfficientRFandMicrowaveAmplifiers

JKAEverard

BroadbandpowerefficientClassEamplifiershavebeendevelopedforusefrom120to180MHz.NewCADtechniquesweredevelopedtoimplementtherapiddesignandevaluationofsuchcircuits.Newcircuitswhichpresenttheoptimumcompleximpedancetotheactivedeviceoverabroadfrequencyrangehavebeendeveloped.Thesedesigntechniquesarenowbeingextendedtoproducehybrid,microstripandMMICversionsoperatingabove900MHzforuseinmobiletelephonesandcommunicationssystems.Distributedloadnetworkshavebeendevelopedwhichproduceefficienciesgreaterthan75%with500mWoutputpowerat1GHz.A'realtime'loadnetworksimulatorhasbeenwrittenwhichallowsfulltuningofthecomponentvaluesandfrequencywhileobservingthewaveformsatallthenodesin'realtime'onanoscilloscopelikedisplay.

MicrowaveBroadbandNegativeGroupDelayCircuits

CBroomfield,JKAEverard

Microwavenegativegroupdelaycircuitsofferingoctavebandwidthshaverecentlybeenproduced-seeElectronicslettersNovember2000,Vol.36,No33.

DynamicSelfRoutingAllOpticalSwitches

JKAEverard,MPage-Jones

AllopticalSwitcheshavebeendevelopedwhichautomaticallyrouteopticaldatasignalswherethedata,destinationaddressandopticalpowerareallcontainedwithinthesingleopticallaserbeam.ThisistheopticalequivalentoftheoldStrowgerExchange.AnewallopticalsystemwithoneinputandthreeoutputshasrecentlybeendemonstratedattheRoyalSocietyusinganinputopticalpowerof300micro-watts.Thisisbelievedtobethefirstallopticalswitchwhichcontainsthedata,destinationaddressandpowerallwithinthesame300microwattI/Plaserbeam. Theswitchoperatesbyautomaticallyproducingadiffractiongratingwithinannonlinearcrystalwhichrotatesaccordingtothedestinationaddress. Thecodingiscarriedwithintheautocorrelationoftheinputsignalwhichinthiscaseisthedistancebetweenadjacentpulses.

Allopticalswitching.

DemonstrationofswitchingbetweenO/P1O/P2

PicosecondOpto-Electronics

JKAEverard,NGhogomu

Ultra-fastopto-electronicdetectorsandmixershavebeendevelopedwithbandwidthsextendingfromDCto50GHz（5psrisetime）.Mostrecentlya3-waveopto-electronicmixerhasbeendemonstratedwhichdetectstwoopticalsignalsspaced33GHzapart.Thesesignalsaredetectedanddownconvertedto500MHzallwithinthesamedevice.MMICversions,asillustratedbelow,havebeenfabricatedandshowntowork.Analysispredictsperformanceoftenbetterthanidealphotodiodes.Thesedevicesarebeingusedforcoherentdetectionanddownconversionandasphasedetectorsforphaselockingsemiconductorlasers.Currentdevicesdemonstrateasensistivityof-60dBm@33GHzina1MHzbandwidthwithaS/N=1.ShotNoiselimitedsubpicoseconddevicesarecurrentlybeinginvestigated.

33GHz3-waveopto-electronicmixer.

OpticalFibreSpectrumAnalysers

JKA.Everard,MPage-Jones

AnopticalfibrespectrumanalyserhasbeenbuiltwhichusesaMichelsonfibreinterferometertomeasuretheautocorrelationfunctionandhencethespectrumofopticalsignals.Theautocorrelationfunctionisobtainedbyusingthestretchingofpolarisationmaintainingfibreinabalancedconfiguration.Differentialdelaysof3cmsinascantimeof50mshavebeenachieved.TechniquesforjoiningAndrewssinglemodeellipticallycoredfibretoDfibrewithtransmissiongreaterthan80%havebeendeveloped.Thisallowedallfibresystemstobebuilt.Thesesystemscanalsobeusedforfibresensorsandforprogrammingtheallopticalself-routingswitches

SupportedbyEPSRC

OpticalFibreSensors

JKAEverard,NGhogomi,RThomas,MPage-Jones

Microwaveradartechniques（SpreadSpectrumRamanOTDR）havebeenusedtodevelopadistributedopticalfibretemperaturesensorcapableofmeasuringthetemperaturedistributionoveraKilometreoffibrewithdegreesensitivityandmetrespatialresolutionasshownbelow.CoherentBrillouintemperaturesensorshavebeendemonstratedandareunderfurtherinvestigation.Newsensorswithsubmeterresolutionarebeingdeveloped.

SupportedbyEPSRCandUniversityofYork

Measurementoftemperatureover1kmusinganopticalfibresensor.

MMICImplementationsofOpto-ElectronicandMicrowaveCircuits

JKAEverard

Oscillators,tunableresonators,filters,highefficiencyamplifiersandphotoconductivethreewaveopticalmixersanddetectorshavebeenbuiltonhybridandmonolithicmicrowaveintegratedcircuits（MMIC's）.Currentlycompleteradiotransmitters（includingthepowerefficientRFamplifier）andreceiversarebeingdesignedonmonolithicmicrowaveintegratedcircuitsandhavealreadybeenbuiltinhybridform.AmicrowaveDopplerRadarisshownbelow.Coherentopticalreceiversanddownconvertersincorporatingthemicrowaveoscillatorsarebeingdesigned.

SupportedbyEPSRC

MicrowaveDopplerRadar.

FutureProjects

RFandMicrowaves:

UltraLowNoiseTunableReferenceOscillatorswithPhaseNoise~-180dBcat10kHzoffsetatXband

BroadTuningLowNoiseVCOs

HighlyPowerEfficientLow