IEEE MTT-V054-I04A (2006-04A)

337 Pages·2006·25.423 MB·English

by  FANTOMASPING

APRIL2006 VOLUME54 NUMBER4 IETMAB (ISSN0018-9480)
PART I OF TWO PARTS
PAPERS
DesignandColdTestingofaRadialExtractionOutputCavityforaFrequency-DoublingGyroklystron ..................
................................... K.Bharathan,W.Lawson,J.Anderson,E.S.Gouveia,B.P.Hogan,andI.Spassovsky 1301
TissueSensingAdaptiveRadarforBreastCancerDetection—InvestigationsofanImprovedSkin-SensingMethod
T.C.Williams,E.C.Fear,andD.T.Westwick 1308
PerformanceAnalysisofSignalViasUsingVirtualIslandsWithShortingViasinMultilayerPCBs .......................
...................................................... S.Nam,Y.Kim,Y.Kim,H.Jang,S.Hur,B.Song,J.Lee,andJ.Jeong 1315
ANovelToroidalInductorStructureWithThrough-HoleViasinGroundPlane....... M.D.PhillipsandR.K.Settaluri 1325
NovelCircuitModelforThree-DimensionalGeometriesWithMultilayerDielectrics .......................................
......................................................................... J.Jayabalan,B.-L.Ooi,M.-S.Leong,andM.K.Iyer 1331
AugmentedHammersteinPredistorterforLinearizationofBroad-BandWirelessTransmitters .............................
.................................................................................... T.Liu,S.Boumaiza,andF.M.Ghannouchi 1340
AFull-WaveNumericalApproachforModalAnalysisof1-DPeriodicMicrostripStructures ..............................
.................................................................... P.Baccarelli,C.DiNallo,S.Paulotto,andD.R.Jackson 1350
Close-in Phase-Noise Enhanced Voltage-Controlled Oscillator Employing Parasitic V-NPN Transistor in CMOS
Process .............................................................................. Y.Ku,I.Nam,S.Ha,K.Lee,andS.Cho 1363
A10–35-GHzSix-ChannelMicrostripMultiplexerforWide-BandCommunicationSystems..... S.HongandK.Chang 1370
ComparisonsBetweenSerpentineandFlatSpiralDelayLinesonTransientReflection/TransmissionWaveformsandEye
Diagrams .................................................................. W.-D.Guo,G.-H.Shiue,C.-M.Lin,andR.-B.Wu 1379
AnalysesofEllipticalCoplanarCoupledWaveguidesandCoplanarCoupledWaveguidesWithFiniteGroundWidth ...
................................................................................. M.Duyar,V.Akan,E.Yazgan,andM.Bayrak 1388
Powerand EfficiencyEnhancement of 3G Multicarrier AmplifiersUsing Digital Signal Processing WithExperimental
Validation .................................................... M. Helaoui,S.Boumaiza,A.Ghazel,andF.M.Ghannouchi 1396
DesignofNewThree-LineBalunandItsImplementationUsingMultilayerConfiguration .................................
.............................................................................. B.H.Lee,D.S.Park,S.S.Park,andM.C.Park 1405
ADigitalDispersiveMatchingNetworkforSAWDevicesinChirpTransformSpectrometers .............................
................................................................................ G.L.Villanueva,P.Hartogh,andL.M.Reindl 1415
CompensationMethodforaNonlinearAmplifierUsingtheGainExpansionPhenomenoninaDohertyAmplifier.......
........................................................................................ H.T.Jeong,I.S.Chang,andC.D.Kim 1425
(ContentsContinuedonBackCover)
(ContentsContinuedfromFrontCover)
MeasurementofFrequency-DependentEquivalentWidthofSubstrateIntegratedWaveguide ..............................
...................................................................................................... C.-H.TsengandT.-H.Chu 1431
Subwavelength-Resolution Microwave Tomography Using Wire Grid Models and Enhanced Regularization
Techniques ........................................................................ B.Omrane,J.-J. Laurin,andY.Goussard 1438
Left-Handed Electromagnetic Properties of Split-Ring Resonator and Wire Loaded Transmission Line in a Fin-Line
Technology..................................... T. Decoopman,A.Marteau,E.Lheurette,O.Vanbésien,andD.Lippens 1451
Wide-BandPredistortionLinearizationforExternallyModulatedLong-HaulAnalogFiber-OpticLinks ..................
.......................................................... V.J.Urick,M.S.Rogge,P.F.Knapp,L.Swingen,andF.Bucholtz 1458
A16-TermErrorModelBasedonLinearEquationsofVoltageandCurrentVariables.......................................
.............................................................................................. K.Silvonen,N.H.Zhu,andY.Liu 1464
IntegratedPlanarSpatialPowerCombiner..................................................................... L.LiandK.Wu 1470
SignalModelandLinearizationforNonlinearChirpsinFMCWRadarSAW-IDTagRequest..............................
..................................................................................... S.Scheiblhofer,S.Schuster,andA.Stelzer 1477
IterativeImageReconstructionofTwo-DimensionalScatterersIlluminatedbyTEWaves...................................
................................................................. D.Franceschini,M.Donell,G.Franceschini,andA.Massa 1484
5.8-GHzCircularlyPolarizedDual-DiodeRectennaandRectennaArrayforMicrowavePowerTransmission............
...........................................................................................................Y.-J.RenandK.Chang 1495
PatchEnd-Launchers—AFamilyofCompactColinearCoaxial-to-RectangularWaveguideTransitions...................
...................................................................................... M.Simeoni,C.I.Coman,andI.E.Lager 1503
AnLTCCBalanced-to-UnbalancedExtracted-PoleBandpassFilterWithComplexLoad ...... L.K.YeungandK.-L.Wu 1512
StudyandSuppressionofRipplesinPassbandsofSeries/ParallelLoadedEBGFilters ......................................
.....................................................................C.Gao,Z.N.Chen,Y.Y.Wang,N.Yang,andX.M.Qing 1519
DesignandExperimentalVerificationofBackward-WavePropagationinPeriodicWaveguideStructures .................
........................................................................ J.Carbonell,L.J.Roglá,V.E.Boria,andD.Lippens 1527
Two-ResonatorMethodforMeasurementofDielectricAnisotropyinMultilayerSamples................... P.I. Dankov 1534
TheEffectsofComponent DistributiononMicrowaveFilters ................................. C.-M.TsaiandH.-M.Lee 1545
ANoiseOptimizationFormulationforCMOSLow-NoiseAmplifiersWithOn-ChipLow- Inductors ...................
..................................................................................K.-J.Sun,Z.-M.Tsai,K.-Y.Lin,andH.Wang 1554
DesignandFabricationofMultibandp-i-nDiodeSwitchesWithLadderCircuits............................................
..............................................................................S.Tanaka,S.Horiuchi,T.Kimura,andY.Atsumi 1561
-BandDual-PathDual-PolarizedAntennaSystemforSatelliteDigitalAudioRadioService(SDARS)Application ....
....................................... Y.-P.Hong,J.-M.Kim,S.-C.Jeong,D.-H.Kim,M.-H.Choi,Y.Lee,andJ.-G.Yook 1569
AComparativeTestofBrillouinAmplificationandErbium-DopedFiberAmplificationfortheGenerationofMillimeter
WavesWithLowPhaseNoiseProperties ......................................................................................
......................... M.Junker,M.J.Ammann,A.T.Schwarzbacher,J.Klinger,K.-U.Lauterbach,andT.Schneider 1576
CompositeRight/Left-HandedTransmissionLineMetamaterialPhaseShifters(MPS)inMMICTechnology ............
....................................................................................J.Perruisseau-CarrierandA.K.Skrivervik 1582
ANewFeedbackMethodforPowerAmplifierWithUnilateralizationandImprovedOutputReturnLoss.................
........................................................................... Z.-M.Tsai,K.-J.Sun,G.D.Vendelin,andH.Wang 1590
SensitivityAnalysisofScatteringParametersWithElectromagneticTime-DomainSimulators.............................
.................................................................................... N.K.Nikolova,Y.Li,Y.Li,andM.H.Bakr 1598
Self-ConsistentCoupledCarrierTransportFull-WaveEMAnalysisofSemiconductorTraveling-WaveDevices .........
.................................................. F.Bertazzi,F.Cappelluti,S.DonatiGuerrieri,F.Bonani,andG.Ghione 1611
Periodic FDTD Analysis of Leaky-Wave Structures and Applications to the Analysis of Negative-Refractive-Index
Leaky-WaveAntennas .................................................. T.Kokkinos,C.D.Sarris,andG.E.Eleftheriades 1619
LETTERS
Correctionsto“Complex-PermittivityMeasurementonHigh- MaterialsviaCombinedNumericalApproaches” ......
........................................................................................... X.C.Fan,X.M.Chen,andX.Q.Liu 1631
Corrections to “Error Correction for Diffraction and Multiple Scattering in Free-Space Microwave Measurement of
Materials” ............................................................................................................ K.M.Hock 1631
InformationforAuthors ............................................................................................................ 1632
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IEEETRANSACTIONSONMICROWAVETHEORYANDTECHNIQUES,VOL.54,NO.4,APRIL2006 1301
Design and Cold Testing of a Radial Extraction Output
Cavity for a Frequency-Doubling Gyroklystron
Karthik Bharathan, Student Member, IEEE, WesLawson, Senior Member, IEEE, James Anderson,
Emmanuel Steven Gouveia, Bart P.Hogan,and Ivan Spassovsky
Abstract—Research in the University of Maryland at College
Park’sGyroklystron(GKL)Projecthasrecentlycenteredaround
the development of a high-power high-gain frequency-doubling
17.136-GHz system. The current tube is a four-cavity (input,
buncher, penultimate, and output) coaxial frequency-doubling
system that will be used to drive a linear accelerator structure.
Thispaperpresentsthedesign,simulation,optimization,coldtest
methodology,andperformancedataofaproposedradialextrac-
tion output cavity in which the microwave energy is extracted
through an inner coaxial conductor in the TE01 circular mode.
Thepositioningofdielectricsinthedriftspacesandtheeffectof Fig.1. UniversityofMarylandatCollegePark’sGKLtestfacilitylayout.Am-
axialandradialmisalignmentsbetweentheinnerandouterwalls plifiedmicrowavesinTE circularmodeexitfromlargeuptaperontheright.
ofthecavitywerestudiedindepth.Oneadvantageofthistopology
isthatitreducesthesizeandcomplexityoftheoutputwaveguide
chainotherwiseneededtoconverttheTE02 circularmodefrom
the GKL into the standard rectangular waveguide mode for
injection into the Haimson Research Corporation accelerator
structure. Cold test results show that this new cavity, which has
a of 458 and a resonant frequency of 17.112 GHz, is a viable
replacementfortheoutputcavitycurrentlyinthesystem,aslong
asthecavityiswellaligned.
Index Terms—Accelerator drivers, gyroklystron (GKL), mi-
crowavecouplingscheme.
I. INTRODUCTION
SIGNIFICANTmilestonesrecentlyachievedintheUniver- Fig.2. PowertransportfromUniversityofMarylandatCollegePark’sGKL
toHRCacceleratorstructure.TheamplifiedoutputsignalfromtheGKLfeeds
sity of Maryland at College Park’s Gyroklystron (GKL) intothelargedowntaperontheright.
Project include a three-cavity first harmonic coaxial system,
whichproducedover75MWofpeakpowerat8.57GHz,anda to condition the four-cavity system to act as a driver for the
three-cavityfrequency-doublingsystemthatproduced27MW acceleratorstructuredesignedanddeliveredtotheUniversityof
at17.14GHz[1],[2].Thelatterservedasastartingpointforthe MarylandatCollegeParkbytheHaimsonResearchCorporation
designofafour-cavityfrequency-doublingsystem[3]thatwas (HRC),SantaClara,CA[4].
expectedtohavealarge-signalgainofabove50dB.Thiswas The HRC accelerator structure employs a compact power
achievedinpartbytheintroductionofanadditionalgaincavity multiplier system based on a dual hybrid feed ( rectan-
(penultimate cavity) before the output cavity. Fig. 1 shows a gular mode) bridge configuration, effectively generating high
schematicofthetestfacilitywherethedifferentGKLtubesare acceleratinggradients[4].Toenabletheexperimentalsystemto
testedandcharacterized.Thecurrentfocusoftheexperimentis beadriverfortheHRCacceleratorstructure,apowertransport
system that connects the output of the GKL ( circular
mode) to the two rectangular WR-62 injection arms of the
ManuscriptreceivedJanuary13,2005;revisedAugust12,2005.Thiswork HRCstructurewasdesignedandfabricated(Fig.2).Theoutput
wassupportedbytheDivisionofHigh-EnergyPhysics,DepartmentofEnergy signalfromthelargeuptaper(whichwouldordinarilyfeedthe
underagrant.
anechoic chamber) is now diverted via a nonlinear downtaper
K.BharathaniswithSprint,Chicago,IL60657USA.
W.Lawson,E.S.Gouveia,andB.P.HoganarewiththeInstituteforResearch toaripplewallmodeconverterthatconvertsthe circular
inElectronicsandAppliedPhysics,UniversityofMarylandatCollegePark, mode into the circular mode. It then passes through a
CollegePark,MD20742USA(e-mail:[email protected]).
pumping cross before entering a compact circular to
J.AndersoniswiththeMassachusettsInstituteofTechnologyLincolnLab-
oratory,Lexington,MA02420USA. rectangular mode converter (Tantawi converter) [5]. A
I.SpassovskyiswiththeFree-ElectronLaserLaboratory,ItalianNational bifurcation then divides the power equally between the two
AgencyforNewTechnologies,Energy,andtheEnvironment,ResearchCentre,
injection arms by converting the rectangular mode into
00044Frascati,Italy.
DigitalObjectIdentifier10.1109/TMTT.2006.871351 a rectangular mode in eacharm. -and -plane bends
0018-9480/$20.00©2006IEEE
1302 IEEETRANSACTIONSONMICROWAVETHEORYANDTECHNIQUES,VOL.54,NO.4,APRIL2006
the downtapering of the output waveguide is minimized will
haveimprovedzero-drivestability.
The axial extraction scheme also necessitates a ripple wall
modeconvertersectiondownstreamtoconvertthe coaxial
mode from the GKL into the circular mode, which is
the desired output mode for accelerator applications that re-
quirepulsecompression(Fig.2).Suchadesignwouldinvolve
a tradeoff between bandwidth and mode purity, in addition to
compensating for any spurious modes generated in the chain
[6].
Thus, an improved extraction scheme would provide for a
methodtoseparatethemicrowavesfromthespentbeamrapidly,
whilesimultaneouslyensuringthatthesignalisextractedfrom
theoutputcavityinamodethatminimizestheneedtosignifi-
cantlyreducetheoutputwaveguidedimensionsandenablethe
systemtobezerodrivestable.
As shown in Fig. 3(b), the radial extraction output cavity is
definedbychangesintheradiiofboththeinnerandouterwalls
[7]. Strong axial magnetic fields at the inner and outer con-
ductingwallsareacharacteristicofthe coaxialmodethat
isexcitedintheoutputcavity.Thismodeismagneticallycou-
pledtothe coaxialmodeintheinnercoaxguidethrough
fourcouplingslotssymmetricallydistributedaboutitsazimuth.
Fig.3. (a)Schematicofatypicalaxialpowerextractionschemewherethe The -field near the slots should be small since, ideally, this
separationofamplifiedmicrowavesandspentelectronbeamtakesplaceinthe field goes to zero at the metal boundaries. The inner coaxial
beamdumpbeyondtheoutputcavity.(b)Schematicofproposedradialpower
structureterminateswithavariableshortontheupstreamside,
extractionoutputcavityinwhichtheamplifiedmicrowavescouplefromthe
cavitytotheinnerconductor. whichcanbeadjustedtoreinforcethesignalpropagatingdown-
stream.Aconicalcoaxialtocylindricaltransitiononthedown-
stream end converts the coaxial mode generated in the
are used to orient the drive signal for the HRC accelerator innercoaxialregionintothe circularmode,whichistrans-
structure,andaphaseshifterisprovidedforphaseequalization portedthroughtheoutputwaveguidesystem.Theupstreamand
ofthesignalsinthedualfeedarms. downstreamboundariesofthemaincavityregionareoccupied
A common feature of various GKL amplifiers, differing in bydriftregionsthatarecut offtothe mode.Thephys-
theiroperatingfrequency,number,andgeometricprofileoftheir ical dimensions of this new cavity need to be comparable to
cavities, cavity modes, and harmonic number is the axial mi- that of the current one to ensure that the tube can be housed
crowavepowerextractionscheme[seeFig.3(a)].Inthisscheme, in its original assembly (vacuum jacket and related hardware)
the amplified microwave signal and the spent electron beam without a major overhaul of the circuit. Additionally, the new
travel together in the output waveguide, where a beam dump cavity would have essentially the same gain and efficiency as
dissipatestheremainingelectronenergy.Intheseschemes,the theexistingoutputcavity.Thevolumeoftheinnercoaxguide
crosssectionofthe outputwaveguidediffersslightlyfrom the iscomparabletothatoftheTantawiconverter,thusavoidingthe
crosssectionoftheoutputcavityandundergoesagradualvari- need for a long problematic downtaper scheme. It would also
ation overan axial distance of several wavelengths. In this re- obviatetheneedfortheripplewallmodeconvertersection,and
gion of the microwave circuit, the electron beam energy is as shouldinsurethezero-drivecapabilityofthesystem.
yet unexhaustedwithessentiallythe same beamcross section,
andremainspotentiallywellcoupledtotheoperatingmodeor II. COMPUTERMODELING
variousspuriousmodes.Thus,reverseenergytransferfromthe The principal dimensions of the current axial extraction
microwaves to the electron beam, which significantly reduces output cavity obtained with GYCOAX and MAGYKL [8]
theefficiencyofthesystem,ispossible. served as the starting point for the radial extraction cavity
Zero-drive instability is a concern because without a drive design. A three-dimensional (3-D) model of the cavity is
signaltoinitiatebunching,thebeamqualityremainsveryhigh generated using Ansoft’s High Frequency Structure Simulator
even after the output cavity. The large reduction in the output (HFSS) [14]. The model includes a WR-62 injection arm for
waveguide dimensions prior to injecting into the accelerator exciting the coaxial mode in the cavity for cold test
structure increases the likelihood of trapped modes in the ta- purposes only. By taking advantage of cylindrical symmetry,
peredsections.Reflectionsmayoccurintheoutputwaveguide a 90 slice of the HFSS model is constructed (Fig. 4), which
oratthewindowwhendowntaperingpushespropagatingmodes requiresthesimulationofonlyoneinjection/probingportwith
belowcutoff.Alongnonlineartaperedwaveguidesectioncould the symmetry cuts defined as perfect electric boundaries. The
actasacavityorasabackwardwaveoscillatorwithalowstart variable short, however, makes the system asymmetric in the
oscillationcondition.Thus,apowerextractionschemeinwhich -direction, necessitating a simulation of its complete axial
BHARATHANetal.:DESIGNANDCOLDTESTINGOFRADIALEXTRACTIONOUTPUTCAVITYFORFREQUENCY-DOUBLINGGKL 1303
Fig.4. Quartered3-DsectionalviewofHFSSoutputcavitymodel.
length.HFSSevaluatesthecoldtestperformanceofthecavity
by simulating the injection of a signal at the drive frequency
through the WR-62 waveguide. The design was optimized by
the variation of several parameters, the primary ones being
the angular width and axial length of the coupling slots, the Fig. 5. HFSS simulated electric field patterns for perfectly aligned output
numberofslots,theaxialpositionofthevariableshort,andthe cavity.(a)z=0cutshowingtheazimuthaldistributionofelectricfields.Note
thickness of the inner wall of the output cavity. The coupling lackofazimuthalvariationindicatingthatitisacircularelectric(TE )mode.
(b)Longitudinalsliceshowingpowertransportincavitystructure.Thedrift
slotswerethemostsensitiveanddifficultelementtodesign,as regionsaredesignedtobecutofftothecavitymode,whichisconfirmedby
theygreatlyinfluencetheresonantfrequencyandqualityfactor theminimalpenetrationofcavityfieldsinthedriftregions.
of the cavity. The is particularly sensitive to fluctuations in
slotlength,varyingbyafactoroftenforaslotlengthchangeof
roughly 0.5 cm. However, the cavity characteristics are not as tolerances that can be introduced in the fabrication process
sensitivetotheazimuthalpositioningoftheslots,ascompared without adversely affecting cavity performance, two cases,
to their axial length sensitivity [15]. Another constraint was which could occur independently or in unison, were investi-
to make the metal conducting gaps between the slots as large gated, namely: 1) a radial offset between the inner conductor
asnecessarytoensuremechanicalstrengthofthesystem.The andtheinserts,resultinginthemhavingdissimilaraxesofsym-
final optimized design called for four slots each having an metryand2)anaxialoffsetoftheinnerconductorwithrespect
angularwidthof81.5 withanaxiallengthof5.08mm. totheinserts,resultinginamisalignmentofthedepressionson
AsseeninFig.5(a),thedoubleradialvariationfieldpattern theinnerandouterradialwallsthatconstitutethecavity.
indicative of the coaxial mode is excited between the Toaccommodatearadialoffsetoftheinnerconductorrelative
innerconductorandouterwall.This,inturn,magneticallycou- totheouterhousing,themodelismirroredintoahalfsection.
ples through the slots to the coaxial mode in the inner The inner conductor is then shifted in steps of, say, 0.05 mm
conductor.Themetalconductinggapsshowupinwhitealong (2mil)alongeitherthe -or -axis,withnoalterationinthe
thecircumferenceoftheinnerconductor.Fig. 5(b)isalongi- positioning.Fig.7(a)showstheelectricfielddistributionacross
tudinal slice of the cavity, which in addition to illustrating the thecavitycenter,whileFig.7(b)indicatesthepowertransport
electricfieldcoupling,alsoshowshowtheconicaltaperconverts throughthestructureforaradialoffsetof2mil,whichwouldbe
the coaxialmodeintheinnerconductorintothe cir- thelimitingradialtoleranceconsideringthedistortionobserved
cularmodefurtherdownstream.Fig.6(a)showsthetheoretical in the cavity modes. This distortion manifests itself in an
transmissioncurveforthecavity,exhibitingaresonantfre- transmission curvewith twodistinctresonant frequencies [see
quencyof17.08GHzanda of354. Fig. 6(b)] staggered in frequency by 75 MHz. A Fourier anal-
Practically, the cold and hot test prototypes of this cavity ysisinvolvingtwoelectricfields(whosevariationasafunction
would be realized using discrete sections for the inner con- of time was represented by an amplitude factor, an exponen-
ductor, outer wall, and the insets. The eccentricities of the tiallydecayingcomponentdependentontheresonantfrequency,
individual cylindrical sections, as well as any relative shift qualityfactor,andarelativephase-shiftterm)yieldedacurveof
or slop could have an unpredictable effect on the cavity per- asimilarnature,whichledustobelievethatthereweretwodis-
formance. To provide clear guidelines on the limits of design tinctcompetingmodesinthemisalignedcavity.
1304 IEEETRANSACTIONSONMICROWAVETHEORYANDTECHNIQUES,VOL.54,NO.4,APRIL2006
Fig.7. HFSSsimulatedelectricfieldpatternsforaradialoffsetof2mil.(a)z=
0 slice shows that the TE cavity mode though visible, lacks perfect az-
imuthalsymmetry.(b)LongitudinalsliceindicatinghowthedistortedTE
coaxialcavitymodecouplesimperfectlytotheTE coaxialmodeintheinner
conductor.
Fig.6. TheoreticalS transmissioncurvesfortheoutputcavity.(a)Perfectly
alignedcase,exhibitingasingleresonancepeakat17.08GHz.(b)2-milradial
offsetcase,exhibitingaprominentpeakat17.08GHzandaspuriouspeak6dB
lowerat17.155GHz.(c)1-milaxialoffsetcase,exhibitingtwopeaksofnearly
equalamplitude,separatedinfrequencyby85MHz. Fig.8. Coldtestbenchsetupoftheradialextractionoutputcavityconnected
totheHP8757Cscalarnetworkanalyzer.
Tosimulate the effect of an axial displacement between the
arenotshown,asthe -fieldisseverelydistortedwiththecavity
inner coax and outer conductor, the quarter symmetry section
modesbarelydiscernable.
is again used to cut down on computation time. Keeping the
and positions of the inner conductor as per the base line
modelconstant,itisthenoffsetaxiallyalong .Thisresultsin III. COLDTESTRESULTS
amisalignmentofthechangesintheradiioftheinnerandouter Fig.8illustratestheexperimentalsetupwhereanaluminum
conductors that define the output cavity. As seen in Fig. 6(c), prototypeofthecavitywascoldtested.Thecavityispositioned
the effectofanaxialoffsetofeven0.025mm(1mil)is much at the center of a 150-mm-long cylindrical support structure.
more pronounced with the transmission curve exhibiting The WR-62 waveguide section that breaches through the
two humps of nearly equal amplitude, staggered in frequency housing is also visible, connected to a detector probe for the
by85MHz.HFSSsimulatedelectricfieldpatternsforthiscase HP8757C scalar network analyzer. Cylindrical inserts, which
BHARATHANetal.:DESIGNANDCOLDTESTINGOFRADIALEXTRACTIONOUTPUTCAVITYFORFREQUENCY-DOUBLINGGKL 1305
serve as the cut off/drift regions fit snugly into this housing.
Eccosorb BSRII/SS-6M, an elastomeric microwave absorber,
wasappliedtothedriftregionstominimizespuriousmodesand
reflections from the walls of the inserts [10]–[12]. The inner
coaxial conductor is rigidly supported between the microm-
eter-drivenvariableshortontheupstreamendandadepression
in the faceplate on the downstream end. A Marié converter
accepts the circular mode and converts it into the
rectangular mode. To mitigate the effect of spurious
modes that may be generated in the process, the converter is
cascadedwitha -modefilter[6].Themodefilterconsists
ofasix-finFiberglassresistancecardwedgedsymmetricallyin
thecylindricalhousing.Apairofcrossguidecouplersareused
tomeasuretheincidentandreflectedpowersinthesetup.
Preliminarytestsshowedadual-humpstructureindicativeof
some degree of misalignment in the cavity housing. The indi-
vidualassembliesthatconstitutethecavitywerefoundtohave
eccentricityrangesbelow0.2milwhenmeasuredonthecoor-
dinatemeasurementmachine(CMM).Thisruledoutthepossi-
bilityofalossofcircularityintheassembliescausingthemode
competitionpredictedearlier.Theupstreamanddownstreamin-
sets,however,werefoundtohaveasmallamountofplaywhen
insertedinthecavityhousing,andthiswascompensatedforby
insertingshimstocktocentertheinsertsperfectlywithrespect
totheinnerconductor.The transmissioncurveofthiscor-
rectedcavityisshowninFig.9(a),whichcloselyapproximates
theHFSSpredictedtransmissioncurveofFig.6(a).Theexper-
imental resonant frequency of 17.112 GHz is 32 MHz higher
thanthetheoreticalestimate,whilethemeasured of458ex-
ceedstheHFSSestimatebyapproximately100.Toverifytheef-
fectofaradialoffsetonthetransmissioncurve,theinsertswere
shimmedwith2-milstocktoexaggeratetheoffsetpresent.The
corresponding experimental transmission curve, shown in
Fig.9(b),exhibitsthefamiliardual-humpfeaturewithapromi-
nent peak at 17.094 GHz and a secondaryresonant peak 6 dB
lowerat17.183GHz.Anaxialoffsetoftheinnerconductorthat
willmisaligntheinnerandoutercavitywalls,canbemimicked
by taking advantage of the compressibility of the O-ring seal
onthedownstreamfaceplate.Astheinnerconductorisrigidly
supportedbetweenthefaceplates,shimstockthatwouldcom-
presstheinsertstowardtheO-ringsealwasinsertedtoproduce
anoffsetof1mil.Fig.9(c)illustratesthetransmissioncurvein
theaxialoffsetcaseinwhichthedualresonantpeaksofnearly
equalamplitude,separatedby71MHz,arevisible.
Fine tuning of the cavity and resonant frequency can be
Fig.9. ExperimentalS transmissioncurves.(a)Correctedcavitywithradial
achievedbyadjustmentoftheaxiallengthofthecouplingslots. andaxialmisalignmentscompensatedfor(b)cavityhousingshimmedtomimic
Theeffectivecouplingslotlengthisprogressivelyreducedfrom 2-milradialoffsetand(c)cavityhousingshimmedtomimic1-milaxialoffset.
itsmaximumof5.08mmtoapproximately50%ofitsoriginal
lengthusingastripofadhesive-backedcoppertapetomaskthe
slots.Theresonantfrequencyand arethenplottedasafunc- placeinthecavityarenotaresultoftheBSRII/SS-6Mabsorber
tion of the slot opening (Fig. 10). The same procedure is sim- in the drift regions. The optimum placement is with the lossy
ulated in HFSS to obtain experimental trends in the resonant materialbackedupapproximately1.35cmawayfromthecavity
frequencyand .Inthecorrectedcavity,thecoldtest of458 lipintheupstreamanddownstreamdriftregions.Applyingthe
observedwiththeslotscompletelyopenisabitoffthepredicted lossy material all the way up to the cavity edge contributes
valueof354.Moresignificantly,however,the experimental to higher losses in the drift regions, which suppresses the
inthecorrectedcavityrisestoapproximately1200withthecou- well below the theoretical value predicted by HFSS. The ex-
plingslotsclosed50%,whichisinkeepingwiththetheoretical perimentalresonantfrequencyplotshowsanupshiftofaround
estimate. This trend is a good indicator that the losses taking 30MHz,ascomparedtothetheoreticalcurve.
1306 IEEETRANSACTIONSONMICROWAVETHEORYANDTECHNIQUES,VOL.54,NO.4,APRIL2006
the circularmode,and obviatethe need forlarge reduc-
tionintheoutputwaveguidedimensionsoraripplewallmode
convertersection.Thus,itwouldbeideallysuitedtoinjectdi-
rectlyintothecompact circularto rectangularmode
converterinthelinearacceleratorstructurefeedchain.
REFERENCES
[1] J.Cheng,X.Xu,W.Lawson,J.P.Calame,M.Castle,B.P.Hogan,V.
L.Granatstein,G.S.Nusinovich,andM.Reiser,“Experimentalstudies
ofahigh-power,X-band,coaxialgyroklystron,”IEEETrans.Plasma
Sci.,vol.27,no.8,pp.1175–1187,Aug.1999.
[2] V.L.GranatsteinandW.Lawson,“Gyro-amplifiersascandidateRF
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6,pp.648–664,Jun.1996.
[3] P.E.Latham,W.Lawson,andV.Irwin,“Thedesignofa100MW,
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[4] J.HaimsonandB.Mecklenburg,“Alinearacceleratorpoweramplifi-
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[5] I. Spassovsky, E. S. Gouveia, S. P. Tantawi, B. P. Hogan, W.
Lawson,andV.L.Granatstein,“Designandcold-testingofacompact
TE (cid:0)>TE modeconverter,”IEEETrans.PlasmaSci.,vol.30,
IV. SUMMARYANDCONCLUSIONS no.6,pp.787–793,Jun.2002.
[6] W.Lawson,M.Esteban,H.Raghunathan,B.Hogan,andK.Bharathan,
“Ripple-wallmodeconvertersforhighpowermicrowaveapplications,”
IEEETrans.Microw.TheoryTech.,tobepublished.
[7] J. P. Anderson, “The advanced-concept gyroklystron design,” M.S.
Inthispaper,wehavecharacterizedthedesignperformance thesis, Elect.Comput.Eng.Dept., Univ. Marylandat CollegePark,
CollegePark,MD,1997.
oftheradialextractionoutputcavityandpresenteditasaviable
[8] E.S.Gouveia,“Developmentofafourcavitysecond-harmonicgy-
solutiontoreplacetheaxialextractionoutputcavitycurrentlyin roklystronasdriverforalinearaccelerator,”Ph.D.dissertation,Phys.
thesystem.Finerpointsontheoperationofthecavity,suchas Dept.,Univ.MarylandatCollegePark,CollegePark,MD,2004.
[9] W. Lawson, “Theoretical evaluation of nonlinear tapers for a high-
thepositioningofdielectricsinthedriftregions,arerevealedin
powergyrotron,”IEEETrans.Microw.TheoryTech.,vol.38,no.11,
thecoldtesting.Italsogivesclearguidelinesonthelimitsofde- pp.1617–1622,Nov.1990.
signtolerancesthatcanbeintroducedinthefabricationprocess [10] J.CalameandW.Lawson,“Amodifiedmethodforproducingcarbon
loaded vacuum compatible microwave absorbers from a porous ce-
without adversely affecting cavity performance. The electro-
ramic,”IEEETrans.ElectronDevices,vol.38,no.6,pp.1538–1543,
magneticparametersofthecavity(resonantfrequency, ,etc.) Jun.1991.
areacutelysensitivetoanymisalignmentbetweentheinnercon- [11] W. Lawson, J. Cheng, M. Castle, B. Hogan, V. L. Granatstein, M.
Reiser, and G. P. Saraph, “High-power operation of a three-cavity
ductorandtheinsertsthatconstitutethecavity.Aradialoffset
X-band coaxial gyroklystron,” Phys. Rev. Lett., vol. 81, pp.
of 2 mil (or greater) between the inner and outer conductors 3030–3033,Oct.1998.
producesadualpeaktransmissioncurve,andamoderatelydis- [12] ECCOSORB-BSRSpecificationSheetEmerson&CumingMicrowave
Products,Randolph,MA,Rev.Rep.,2002.
tortedfieldstructureoftheexpected coaxialmode.The
[13] Microwave Div., Elisra Electron. Syst. Ltd.. Bene Beraq, Israel,
differencebetweentheamplitudesoftheresonantpeaksis,how- YEAR.
ever, in excess of 5 dB, allowing for sufficient discrimination [14] HighFrequencyStructureSimulator(HFSS).ver.9.1,Ansoft,Pitts-
burgh,PA,2004.
betweenthe two.Theeffectofa 1-milaxial misalignmentbe-
[15] K.Bharathan,“Coldtestingofaradialextractionoutputcavityfora
tweentheinnerconductorandtheinsertsismorepronounced. frequencydoublinggyroklystron,”M.S.thesis,Elect.Comput.Eng.
It is characterized by two competing modes, a distorted field Dept.,Univ.MarylandatCollegePark,CollegePark,MD,2004.
structure of the mode, and nearly equal amplitude of
the two resonant peaks. The experimentally determined reso-
nant frequency of the cavity compensated for radial and axial
misalignmentsis17.112GHz,whichis32MHzhigherthanthe
theoretical HFSS predicted frequency of 17.08 GHz. The cor-
responding cold test measured is 458, which is higher than
thetheoretical byapproximately100.Thesimulationproce- Karthik Bharathan (S’00) was born in Bombay,
India.HereceivedtheB.E.degreeinelectronicsand
duretoextractcavityparametersfromHFSSisinherentlydiffi-
telecommunicationsfromtheUniversityofBombay,
cultand,hence,itspredictedcavityperformanceshouldnotbe Bombay,India,in2002,andtheM.S.degreeinelec-
treated as an exact result. They serve as guidelines for the de- tricalengineeringfromtheUniversityofMaryland
at College Park, in 2004. His thesis concerned the
signofacoldtestpiece,whichcansubsequentlybefinetunedto
coldtestingofaradialextractionoutputcavityfora
obtainexactcavitydimensionsforadesiredresonantfrequency frequency-doublingGKL.
and . From2002to2004,hewasaResearchAssistant
withtheInstituteforPlasmaResearch,Universityof
Thiscavityshouldenablethesystemtobezerodrivestable,
MarylandatCollegePark.HeiscurrentlyanAsso-
permitextractionoftheamplifiedmicrowavesfromtheGKLin ciateRFEngineerwithSprint,Chicago,IL.
BHARATHANetal.:DESIGNANDCOLDTESTINGOFRADIALEXTRACTIONOUTPUTCAVITYFORFREQUENCY-DOUBLINGGKL 1307
WesLawson(S’84–M’85–SM’97)receivedtheB.S. Bart P. Hogan was born in Bethesda, MD. He
degree in mathematics and B.S., M.S., and Ph.D. receivedtheB.S.degreeinmechanicalengineering
degrees in electrical engineering from the Univer- fromtheUniversityofMarylandatCollegePark,in
sity of Maryland at College Park, in 1980, 1980, 1986.
1981,and1985,respectively.Hisdoctoralresearch Heworkedbrieflyinindustrybeforejoiningthe
concerned theoretical and experimental studies of InstituteforPlasmaResearch,UniversityofMary-
microwavegenerationinvariouslarge-orbitgyrotron landatCollegePark.HeiscurrentlyaResearchEn-
configurations. gineerwiththeInstituteforResearchinElectronics
From 1978 to 1982, he was with the Electronic andAppliedPhysicsonAdvancedAcceleratorTech-
SystemsBranch,HarryDiamondLaboratories.For nologies,UniversityofMarylandatCollegePark.His
thepast20years,hehasbeenwiththeLaboratoryfor otherareasofinterestincludeenergy-efficientbiome-
PlasmaResearch,UniversityofMarylandatCollegePark,whereheiscurrently chanicaltechnologiesandultraefficientcompactlightingtechnologies.
aProfessorwiththeDepartmentofElectricalEngineering.Hisprincipalinterest
liesinnovelfast-wavemicrowavesources.Hisrecenteffortshavebeendirected
towardhigh-powerfast-waveandhybridamplifiersandassociatedhigh-power
microwavecomponents.
JamesAndersonreceivedtheB.S.degreefromthe
UniversityofWisconsin–Madison,in1995,theM.S.
degreefromtheUniversityofMarylandatCollege
Park,in1997,andthePh.D.degreefromtheMassa-
chusettsInstituteofTechnology(MIT),Cambridge,
in2005,allinelectricalengineering.
Heperformedexperimentalstudiesonhigh-power Ivan Spassovsky received the Ph.D. degree in
gyrotron oscillators with the Plasma Science and physicsfromtheUniversityofSofia,Sofia,Italy.
Fusion Center, MIT, during his doctoral studies. His earlier research withthe University of Sofia
He is currently with the MIT Lincoln Laboratory, concentrated on the physics and applications of
Lexington, MA, where he is involved with radar intenseelectronbeamsandhigh-powermicrowaves.
technologyusinghigh-powermicrowavedevices. From 1992 to 1993, and 1998, he was with the
Plasma Physics Laboratory, Instituto Nacional de
Pesquisas Espaciais (INPE), São Jose dos Campos
Emmanuel Steven Gouveia received the B.S. SP,Brazil,wherehewasinvolvedwiththeresearch
degreeinphysicsfromtheUniversityofOklahoma, and development of 35-GHz gyrotrons. In 1995,
Norman,in1993,andtheM.S.andPh.D.degreesin heheldatwo-yearcontractwiththeLaboratoryfor
physicsfromtheUniversityofMarylandatCollege Quantum Optics, Korean Atomic Energy Institute (KAERI), Daejon, Korea,
Park,in1997and2004,respectively. whereheparticipatedintheconstructionofmicrotron-drivenfarinfraredfree
From1997to1999,hewasinvolvedwithhigh-en- electron laser (FEL). In 1999, he joined the Institute for Plasma Research,
ergy physics as a member of the D0 collaboration University of Maryland at College Park, as a Visiting Researcher, where he
withtheFermiNationalAcceleratorLaboratory.He remaineduntil2002,duringwhichtimehewasinvolvedwiththeexperimental
iscurrentlyaResearchAssociatewiththeGKLpro- evaluationofasecondharmonicGKL.HeiscurrentlyaResearcherwiththe
gramattheUniversityofMarylandatCollegePark. Free-ElectronLaserLaboratory, ENEA ResearchCentre, Frascati, Italy. His
Since1999,hehasbeeninvolvedinhigh-powermi- majorresearchinterestsfocusondevelopmentofterahertzfree-electronlaser.
crowaveresearch.Hisresearchinterestsincludegyro-devicesandnovelaccel- HealsoparticipatesintheSPARCproject,whichisafirststageofresearchand
eratorconcepts. developmentactivitytowardX-rayFELsources.