A Low-Cost Cooperative Engagement Capability Array Antenna · commercial market pull of the...

172 JOHNSHOPKINSAPLTECHNICALDIGEST,VOLUME23,NUMBERS2and3(2002)

C. R. MOORE, M. H. LUESSE, and K. W. O’HAVER

A

ALow-CostCooperativeEngagementCapabilityArrayAntenna

Craig R. Moore, Mark H. Luesse, and Kenneth W. O’Haver

sTechnicalDirectionAgentfortheCooperativeEngagementCapability(CEC),theAirDefenseSystemsDepartmenthasdevelopedalow-costplanarantenna(LCPA)conceptthatprovides foramajor reduction inacquisitionand life-cyclecostsover thecurrentCECarrayantenna.Thenewdesignconceptalsoprovidesenhancedshipboardintegration flexibility and resolves DDG 51 installation challenges associated with thepreexistingCECantenna.Theconceptisafour-faceplanararraysystemthatuseslow-costcommercial-basedarraytechniques.Severaltransmitandreceivemodulesandasmallarraysectionhavebeendesigned,fabricated,andtestedtodemonstratetheefficacyoftheLCPAconcept.TheconcepthasbeentransitionedtotheCECDesignAgent,RaytheonCompany,whichiscurrentlydevelopinganLCPAdesignthatisplannedtoyieldthefirstproductionunitsin2003tosupportDDG51FlightII/IIainstallations,andsubsequentlybecomethebaselineCECshipboardantenna.

INTRODUCTION The Navy’s Cooperative Engagement Capability

(CEC) provides a means by which radar measurementdatafrombattlegroupradarsaresharedinrealtimetoformacompositeairpictureandtoenablecooperativeengagementswheredifferentunitssupportoneanother’smissileoperations.1CriticaltoattainingCECobjectivesis a secure communications system with an unprece-dented response time, high data rate, countermeasuresand radio-frequency (RF) fade resistance, and terminaltrack accuracy to support gridlock alignment. Phasedarray antennas are needed to meet these system-levelrequirements in a directive point-to-point networkingtopology. These moderately high-power phased array

antennasaremajorcontributorstoCECsystemacquisi-tionandlife-cyclecosts.

AsTechnicalDirectionAgentforCEC,APL,work-ing in conjunction with the Navy’s Design Agent,Raytheon Company, has played a leading role indeveloping array antenna systems for CEC. Figure 1summarizes CEC array development, including thecurrent AN/USG-2 shipboard cylindrical active arrayas well as a new-generation low-cost planar antenna(LCPA)currentlyunderdevelopment.

EarlyCECantenna/transmitterequipment,originallydevelopedduringthelate1980sandrefinedintheearly1990s, used a below-deck traveling wave tube–based

JOHNSHOPKINSAPLTECHNICALDIGEST,VOLUME23,NUMBERS2and3(2002) 173

LOW-COST CEC ARRAY ANTENNA

transmitterandamast-mountedcylindricalphasedarrayantennathatapplied“positive-intrinsic-negative”diodephase-shiftertechnology.Thisconfiguration,partoftheAN/USG-1CECequipmentset,wasusedforCECini-tialoperationalcapabilityin1996.Inthemid-1990s,anactivecylindricalarrayantenna,whichbecameknownas the shipboard active aperture (SBAA), was devel-oped.TheSBAAusesgalliumarsenide(GaAs)mono-lithicmicrowave integratedcircuit (MMIC) transmit/receive (T/R)module technology to realize the trans-mitterfunctionwithintheantenna,thuseliminatingalargeamountofbelow-deckequipmentthatwasassoci-atedwiththeprevioustube-basedtransmitter.

IntroductionoftheSBAAresultedinasystemweightsavingsof4000lb,reducedprimepowerrequirements,and greatly improved system reliability. The SBAA,part of the AN/USG-2 equipment suite, was success-fully demonstrated as part of CEC initial operationaltestandevaluationin1997andoperationalevaluationin2001,andiscurrentlyinlow-rateinitialproductionatRaytheon.TheSBAAwasthefirstNavyactivearraytobefieldedonboardshipsandhasdemonstratedexcel-lentperformanceandreliabilityatsea.

Despite the advances of the SBAA, there was astrong desire to reduce the active antenna total own-ershipcost(whichincludesacquisition,operation,andsupportcosts)tosupportFleet-widedeploymentaswellasnewCECapplications.Forexample,theinstallationof two cylindrical SBAA antennas would be requiredontheUSSArleigh Burkeclass(DDG51)FlightII/IIadestroyers. Clearly, this would be a costly approachgiven the large quantity of DDG 51–class II/IIa shipsslatedforinstallation.AcriticalneedexistedforaCECarrayantenna system thatwouldprovide the requiredflexibleDDG51installation,andsignificanttotalown-ershipcostavoidancerelativetoasingleSBAA.

In1998,APLbeganexploringwaystoachievetotalownershipcostavoidance.Alsothatyear,theLabora-toryconceivedafour-faceplanarvariantoftheSBAAthatcouldprovidefortheinstallationflexibilityontheDDG51.However,theprojectedacquisitionandlife-cyclecostsforthecylindricalSBAAanditsplanarvari-antstillexceededdesirablelevels.AfreshapproachtoreducingCECarrayantennacostswasneeded.

One conclusion drawn from these initial conceptdevelopmenteffortswasthatthefour-faceplanararraysolutiontosupportDDG51installationofCECwouldalsobeconducivetofutureshipclassessuchasDDX,whichwereconsideredtobeunlikelytosupportcylindri-calmast-mountedantennas.Itwasalsoclearfromongo-ingCECaswellasotherNavyshipboardantennadevel-opmenteffortsthatsolid-stateactivearraytechnologywasthemostlikelyapproachtoaddressshipboardreli-ability, maintainability, and availability requirementsandassociatedoperationalandsupportcostgoals.

LOW-COST ARRAY DESIGN APPROACH

Anecdotalevidencefromfieldedphasedarrayantennasystems, includingtheCECSBAA,indicatesthattheT/Rmodulesaccountfor30to50%oftheproductionacquisition cost of such systems. T/R modules havehistorically cost DoD from $1,000 to $10,000 each,depending on the performance requirements, designcomplexity, and quantities purchased. Clearly, reduc-ingthecostoftheT/Rmodulewouldbeanimportantaspect in lowering the production acquisition cost ofaphasedarrayantenna.Notingtheretailpriceofcel-lular telephones or pagers in the last few years leadsonetobelievethatlow-costmodulesarefeasible.Thecommercialmarketpullof thewireless revolutionhas

(a) (c)(b)

Figure 1. A historical perspective of CEC array antenna development. (a) The AN/USG-1 CEC equipment set, originally developed in the late 1980s and refined in the early 1990s, included a mast-mounted cylindrical array antenna and a below-deck tube-based transmitter. (b) The conical mast-mounted shipboard active aperture, part of the AN/USG-2 CEC equipment set, was developed in the mid-1990s and used MMIC-based transmit/receive modules (inset). (c) The four-face low-cost planar antenna is currently under development and planned for Fleet introduction in 2003.



spurredthedevelopmentofexcellentlow-costproductswhosetechnologiesshouldbereadilyadaptabletotheCEC application. However, what performance differ-ences and purchasing practices that make these con-sumerproductslowincostwouldneedtobeadopted?

The LCPA concept was developed to address critical Navy needs for CEC antenna total ownership cost reduction and flexible ship-board integration of a single CEC antenna system.

Cellularphonesoperateintheultrahighfrequencyrange,notthemicrowaveregimeofCEC.Furthermore,thetransmitter inacellularphoneis limitedtoabout1Wofoutputpower,ratherthanthesignificantlyhighervalueofanSBAACECshipboardmodule.Finally,cellphone handset sales are reported to have been morethan400millionin2000.2TheneedforCECmodulesfor the next 20 years would be at least 3 to 4 ordersofmagnitudelessthanthatnumber.WeexaminedtheimplicationsofeachofthesefactorstoapotentialCECT/Rmodule.

The cost of a MMIC amplifier is not appreciablyaffected by the operating frequency. In fact, manylower-frequencycellphonepoweramplifiersaremadethroughapseudomorphichighelectronmobilitytran-sistor(pHEMT)MMICprocesstoachievehighdirectcurrent(DC)-to-RFefficiency,andthusprovidelongertalk time on a single battery charge. The telephonemanufacturer is unconcerned with the fact that thepHEMT process was originally developed, with DoDsupport, to achieve improved MMIC device perfor-manceatmicrowaveandmillimeter-wavefrequencies.Whatdoesaffectcostistheoutputpowerrequirementof a MMIC amplifier. Higher output power requireslargertransistors,whichoccupymorechiparea.Largerchipsmeanfewerchipsperwaferinmanufacturing,andthus higher cost per chip. The cost per unit area ofMMICchipsdependsheavilyonthenumberofwafersmanufacturedwithagivenprocesstype,aswellastheyieldofacceptablechipsfromawafer.AheavilyloadedMMICfoundryprocesswillhaveachievedthemanufac-turingefficienciesrequiredtomakeandkeepitcompet-itiveinthemarketplace.ItmatterslittletothefoundryprocessthatMMICchipsarebeingmadefromdifferentdesignmasksfordifferentoperatingfrequencies.Thus,amajor factor in loweringtheproductioncostofT/RmodulesforCECistousecommerciallyviableMMICprocessesataheavilyloadedfoundrywhileusingahigh-yieldingdesignthatkeepstheMMICchipssmall(i.e.,lowpower).

TherelativelylowquantitiesofMMICchipsneededfor CEC are not an impediment to low cost if com-mercially successful foundry processes are employed.However, the rapid pace of change in the consumertelecommunicationsindustrymakestheissueofcompo-nentobsolescenceacertainty.Consumerproduct life-timesaremeasuredinmonths,whereasaCECantennasystemislikelytobeinproductionfor6ormoreyears,withsparesrequirementsforatleast20years.Onesolu-tiontothisproblemistomakealifetimebuyofMMICchips before the foundry process is bypassed by thecommercial market. Another approach is to embracetheevolutionofcommercialdevelopmentsandplantoupgradetheMMICdesignperiodically totakeadvan-tageofimprovedperformancewhilecontinuingtousecommercially viable foundry processes that offer lowproductioncosts.

AcommerciallysuccessfulMMICchiprequiressev-eral design iterations to optimize performance againstthe process limits and tolerances to ensure consistenthighyield.Becauseadesign iterationcan take3 to5monthsandcostmorethan$100,000,itisnotunusualfor a new MMIC design to require 12 months and$500,000fordevelopment.BecauseaT/Rmodulecon-tainsthreeormoreuniqueMMICchips,thenonrecur-ringengineeringanddevelopmenttimecanbeconsid-erable.Ifcommercialof-the-shelf(COTS)MMICchipscanbeused,thedevelopmentcostscanbeavoided.Inaddition,asuccessfulCOTSMMICchipimpliesthatitismanufacturedonahighlyloadedfoundryprocesslineatconsistentlyhighyield.Asacorollary,amodificationtoCOTS(MCOTS)MMICdesignislikelytoyieldalesscostlysolutionthanafullcustomdesign.

MMICchipcostonlyaddresses30to50%oftheT/Rmodulecost.Otherfactorsarethepackageorhousingwiththerequisiteconnectors,othercomponentsinthemodule, assembly and test labor, and rework labor orscrapcostifyieldatfinaltestispoor.Severalcostben-efits accrue if the functionality of the module is keptsimple:

• Boththequantityofotherneededcomponentsandthesizeofthepackagearereduced.

• Assembly and test labor is more readily reducedthroughautomation.

• Highfirst-passmoduleyieldatfinaltestismoreeasilyachieved.

Therearealsolow-costalternativestoconventionalRFand digital control connectors, and these are heavilyusedinconsumerelectronicsproducts.

Anumberoflarge,highlyautomatedfactorieswererequiredtoproducethe400millioncellphonesin2000.SignificantproductionoutsidetheUnitedStatesisalsopresumedinthisendeavor.Clearly,this isoutsidetherealmofanyCECsolutiontomoduleproduction.Theoptimumproductionrateofamodule factorydepends



onthetypeofprocessforwhichitwasdesigned.Somefactoriesaredesignedforbatchproductionofshortpro-duction runs and are therefore adept at changing theautomatedequipmentquicklytoanotherproduct.How-ever, theproduction rateof these types of factories islimitedbecausetheversatilityoftheautomatedequip-ment comes at the expense of production speed andattendantlabor.Otherfactoriesaredesignedtorunathighproductionratesforlongperiodswithlittlehumanintervention.Downtimetoreconfiguretheequipmentforanotherproductcanbeexpensiveinthesefactories.Additionally,significanttoolingchargesareincurredtoadapttheproducttotheequipment.Asaruleofthumb,theminimumproduction rate for running three shiftsperday,7daysaweek,onasmall-sizelineofthistypeis10,000unitspermonth(about15unitsperhour).

The current CEC shipboard antenna requires about100 T/R modules. An order for 10 systems plus sparesrequires a production run of less than 1500 modules,whichisappropriateforabatch-typeproductionlinebutnotahigh rate line. If a low-cost antennawouldneed1500 modules per system, an order for 10 systems plusspares might require a large enough production run topersuadeahigh-ratemanufacturer tooperate the smallline for6to8weekseachyeartomakeCECmodules.Runningonthistypeoflineshouldresultinsignificantlaborcostsavings.Thegoalshouldbetokeepthelaborcosttolessthan25%ofthetotalmodulecost.Useofanindustrystandardstylepackageandcommerciallyviableconstruction technologies should reduce process devel-opmentandtoolingchargesformodulemanufacture.

Theargument forusingCOTSorMCOTSMMICchipscanbeappliedtootherarraycomponentsaswell.One major item in this category is the power supply.Many choices are now available for modular suppliesthat meet military requirements, but are built side bysidewithindustrial-gradeunitsonautomatedassemblylines.TheseunitshavebeendevelopedinresponsetocommercialdemandfordistributedDCpowerincom-puting and data communications systems. The use ofcommerciallyviableproductionprocesses is alsovalidforprintedwiringboards,wheremultilayerboardscon-tainingbothRFanddigitalcontrolcircuitrycanbeinte-grated inoneprocess.By tailoring thearraydesign tomakeuseofcommercialprocesscapabilities,theecono-miesofscalefromtheconsumerelectronicsmarketcanaccruetomilitaryprogramslikeCEC.

Another key to achieving low production costs isto limit manual or touch labor through higher levelsof integration, application of commercial electronicpackagingdesigntechniques,anddesignforautomatedhigh-volumeassemblyprocesses.Thesetechniquescanbe implemented in an array design by combining RFbeamforming, DC power, and digital control distribu-tion manifolds into a single multilayer printed circuitboard (PCB) that is manufactured with commercial

high-volume production processes. This concept canpotentiallybeextendedtoincludethearrayaperturebyconstructing patch radiating elements and their feedsasadditionallaminationsofthePCB.Electronicmod-ulessuchasT/Rmodulescanbeattachedviaautomatedpick-and-placeequipment.Thesetechniqueswilldra-maticallyreducepartscount,cabling,andinterconnectsandshouldsignificantlyreducematerial,assembly,andintegrationcosts.

Finally,theantennadesignshouldbemodular.Thisallowsmultiplesofasinglelinereplaceableunit(LRU)to be manufactured, achieving production economiesofscale,andsimplifiesmaintenanceandspares.Carefulattentionmustbepaidinpartitioningfunctionalitytooptimize the reliability and cost of the LRUs, exploitthegracefuldegradationinherent inanarray,anduseadditionalredundancyonlywhereneededtomeetreli-abilityrequirements.

CEC LOW-COST ARRAY DESIGN CONCEPT

The argument has been made that low-cost arrayscanbeachievedwithsimple,low-powermoduledesignsusingcommercialprocessesinhigh-volumeproductionandimplementedinhighly integratedarraysubassem-blies.Canlower-powermodulesbeusedtoachieveafullperformance-compliantCECarrayantenna?Theprin-cipal system requirement driving the sizing of a CECarray,andthusitscost,istheeffectiveradiatedpower(ERP). For an active array, there is a classic trade-offbetweenthemodulepowerandthenumberofmodulestoachievetherequiredERP.TheERPisproportionaltothemodulepowertimesthesquareofthenumberofradiatingelementsormodules.

ERP∝PmNe2 ,

wherePm=modulepower,andNe=numberofelementsandmodules.

Althoughwithalower-powermodulemoremodulesarerequiredtoachieveaspecifiedERP,therelationshipisnotlinear.Asmoremodulesareadded,bothgainandpower increase. In parametrically investigating modulepowerandelementcountforERP-compliantCECarrays,itwasfoundthat,assumingachievablefront-endlosses,reasonableCECarraysizescouldbeobtainedwithtrans-mit modules on the order of 1 to 2 W. Low-powermodules were indeed a viable alternative for CEC andprovide for module quantities suitable to high-volume,low-costproductionlines.(Theabovetrade-offisappli-cation-specific.Forexample, a low-powermodule solu-tionisattractiveforamoderate-powercommunicationslink such as CEC, but not necessarily for high-powerradars.)



Following the low-costdesignapproachoutlined,anewfour-faceplanarCECantennadesignconceptwasconceived. In performing design-to-cost optimizationstudies,costcomparisonspreadsheetswereusedtocom-pare the SBAA antenna architecture to alternativeswithlower-powerT/Rmodulesandwithseparatetrans-mitand receivemodules.This study indicated thatatpowerlevelsbelowabout1Wpermodule,theantennacoststartedtoriseowingtoincreasedstructure,higherLRUcount,andmorecomplexcontrolandsignaldis-tribution. It was found to be advantageous to imple-ment each array face with separate transmit andreceiveaperturesinacommonphysicalenclosure.Thisapproachgreatlysimplifiedmodulecomplexity,leadingtolowerestimatedmoduleproductioncosts;enabledahighlyintegratedimplementationsuitabletocommer-cial printed wiring board fabrication techniques; andsimplified implementation of independent amplitudeweightings for transmit and receive sidelobe control.This new antenna concept, the LCPA, is illustratedinFig.2.ThearrayprimarilycomprisessubarrayLRUsthat are combined in the horizontal plane. For ship-boardreliabilityandmaintainability,thesubarrayLRUsaretobedesignedforhighreliabilityandeasyreplace-ment.TheseLRUs,alongwithotherancillaryelectron-ics,arehousedinanenclosurewhichiscommensuratewith the shipboard environment and suitable in sizefor installationon intended ship classes.Aprotectiveradomeisusedtocovertheradiatingapertures.

Simplified COTS-Based T/R ModulesAchievingverylowmoduleproductioncostiscriti-

cal to meeting the LCPA cost objectives. As a com-municationssystem,therequirementsthatflowtothe

CECT/Rmodulesarelessstringentthanthosetypicallyrequired inmilitary radars.As a result, thesemodulesarefunctionallysimplerelativetoconventionalmilitaryT/R modules. The receive modules contain a phase-shifterMMIC,apostamplifierMMIC,andalownoiseamplifier(LNA)MMIC.Similarly,thetransmitmoduleconsists of a phase-shifter MMIC, a driver amplifierMMIC,andapoweramplifierMMIC.Ineachmodule,ashift-and-storeregister,realizedasasiliconICinchipform,isincludedtotranslateserialdataintoaparalleldataformattocontrolthephase-shiftersettingandturntheDCpoweronoroffinthemodule.AnattenuatorMMIC is not needed in the receive modules becausetheamplitudetaperforsidelobecontrolisachievedinthe beamformer. The transmit modules do not needanattenuatorbecausethemoduleswillbeoperatedingaincompressionforalloperatingmodes.Lower-powermodesareaccommodatedbyturningoffsomemodulestothinthearray.Furthermore,sideloberequirementsdonotdrivethemodulestostringentamplitudeandphaseerror levels. The phase calibration constants for eacharray element will be kept in the subarray-leveldigital control electronics rather than in individualmodules.Thus,theserelativelysimplemodulescontainonly 3 MMIC chips, 1 digital IC, 2 transistors forDC bias on/off, and a few resistors and capacitors,in contrast to the SBAA T/R module, whichcontains8MMICs,3 silicon ICs, andabout80othercomponents.

AcatalogsearchwasundertakentoidentifyCOTSMMICs appropriate to the CEC application. It wasdeterminedthatallrequiredfunctionswereavailableofftheshelf.AnLNA,phase-shifter,postamplifier,poweramplifier, and driver amplifier were each identified asavailableinMMICform.

Because T/R modules account for about a third oftheantennacost,carefulattentionwaspaidtodevelop-ingproductionmodulecost estimates.For theLCPA,module cost is critically important to meeting theantennacostobjectivebecauseofthelargequantityofrelatively low-cost modules used in an antenna. Theapproachwastoestimatethecostofthecomponentsinthemoduleandthepercentageofthecostineachlaborcategory.

TheMMICcost is estimatedusing the total areaoftheMMICchipsandavalueof$2.50/mm2ofchiparea.Theraw,unyieldedchipcostatcommercialfoundriesisgenerallylessthan$1.00/mm2forMESFETprocesseson4-in.waferspurchasedin500-waferquantities.FactoringintypicalDC,RF,andvisualyieldsandaddingthecostofwafer testing andchipdicing andpacking results intypicalMMICcostsof$1.50to$3.00/mm2.Thesecostswillbe further reducedasGaAs foundries transition to6-in.waferstoincreaseproductionvolume.

AGaAsMMICchipareaof11.5mm2wasassumedfor the transmit module and 8.5 mm2 for the receive

Figure 2. The low-cost planar antenna concept, showing sepa-rate transmit (yellow) and receive (green) apertures and the mod-ular subarray implementation.



module,resultinginMMICcostestimatesof$28.75and$21.25, respectively.The silicon ICandcontrol tran-sistors in each module were estimated at $3.25 total,and the module housing (identical for transmit andreceivemodules)at$12.00.Theseestimatesarebasedon vendor budgetary and rough order of magnitudequotes obtained when material was purchased for theconceptevaluationmodulesdiscussedbelow.Thecostof other parts in the modules was estimated at $6.00eachforthetransmitmoduleand$8.00forthereceivemodule.

Assemblyandtestlaborwasestimatedat25%ofthecost of eachmodule and engineering support labor at10%. An additional category, yield contingency, wasincludedat10%toaccount for the fact thatmoduleswhichfailfinaltestarenottobereworked.Thisexer-ciseresultedinahigh-volumeproductioncostestimateof$100forthetransmitmodulesand$89forthereceivemodules.Theseareaggressivecostestimatesthatassume200,000 transmit and60,000 receivemodulesorderedatonetime.Phasedordersoccurringoverseveralyearsmayincreasethecostby2to3timestheseestimates.Itshouldberememberedalsothatthisisacostestimateandnotanegotiatedpricetothegovernment.

Subarray Architecture TileThesubarrayLRUs,whichincorporatetheradiating

elements, transmit and receive modules, distributionmanifolds, and digital control electronics, are imple-mentedinahighlyintegratedtilearchitecture(Fig.3)thatiscriticaltoachievingthecostobjectives.

The patch-radiating elements and their feeds arerealized in a multilayer PCB assembly. This aperture

board mounts onto one side of a cold plate, and thetransmit and receive modules mount to the oppositeside of the cold plate. The modules are packaged inCOTS-derivedhousingsthataresmallenoughtoeasilyfitwithinthelatticespacingoftheradiatingelements.Interconnections between the radiating elements andthetransmitorreceivemodulesareachievedbycoaxialfeedthroughs.Thecoldplateservesasastructuralback-bone, provides critical alignment of all components,and provides cooling for the modules. The apertureboardandcoaxialfeedthroughsprovidespacetoaccom-modate receive protectors and bandpass filters for thereceive elements and ferrite isolators and low-pass fil-tersforthetransmitelements.Theseitemsareneededtoprotectsensitiveactivedevices inthetransmitandreceivemodulesfromtheharshshipboardelectromag-neticenvironment.

AsecondmultilayerPCBmountstothemodulesideofthecoldplate.ThisdistributionboardaccommodatestheRFmanifold(beamformer)andDCpoweranddigi-talcontroldistributionsandprovidesRF,DC,anddigi-tal connections to the modules through conventionalsoldertableads.Thismultilayerboardhascutoutssoitcan mount to the cold plate without interfering withthemodules.Finally,thedigitalcontrolelectronicsarehousedonathirdboardthatoverlaysthemodulesandconnectstothedistributionboard.

Acriticalaspecttoachievingthelow-costsubarrayarchitecture is theuseof connectorless interconnects.The modules, for example, contain no connectors.Themodule-to-apertureboardinterconnectisachievedwith a pogo pin approach. A glass-sealed coaxial pinwitha50-characteristicimpedanceisplacedthroughthe bottom of the module package to act as an RFfeedthrough.Acompressionpin, i.e., thepogopin, isemployedasthecenterconductorinalengthofcoaxiallinethatpassesthroughthecoldplate.

Thepogopinconsistsofapairofconcentric tubeswith a small internal coil spring that pushes on theinnertubetocauseittoprotrudefromtheoutertube.Thisassemblyhasthesamediameterastheinnercon-ductorofastandardsemi-rigidcoaxialcable(0.5mmor0.020in.).Aholedrilledthroughthecoldplateisfilledwiththedielectrictubefromapieceofsemi-rigidcoax-ialcable,andthepogopinisinsertedinthecenterholeof the dielectric to form a 50- coaxial feedthrough.Theexposedpinonthebottomofthemodulepressesagainst thepogopinas themodule isattached to thecold plate, thus making an RF connection as well aslocatingthemoduleonthecoldplate.Theotherendofthepogopinpressesontoaprintedtraceontheaper-ture multilayer board to provide a connection to theantennaelement.

PogopinsaremanufacturedinlargequantitiesforuseinverylargePCBtestfixtures.Consequently,thesepinscost less than $1 apiece when purchased in quantity.Figure 3. Conceptual view of the LCPA tile architecture.

SubarrayLRUs

Radome and frequency-selective surface

Aperture and interconnectmultilayer board

Cold plate withpogo pins

RF-distributionmultilayer board

Transmit or receivemodules

Fuzz button plates

Digital controlmultilayer board



When compared with $5 to $15 per mated pair for ablind-mateRFconnector,thisisalow-costinnovationthathasnotgoneunnoticedbydesigners forthecon-sumerwirelessmarket.

Theconnectionbetweenthemodulesandthedistri-bution board can be achieved in one of two ways. Inthefirstapproach,theotherRFconnection,alongwiththebiasandcontrolsignals,ismadeinaconventionalmanner.Flatleads,whichprotrudefromonesideofthemodulepackage,aresolderedtotheexposedtracesontheedgeofacutoutintheRF,DC,andcontroldistri-butionboard.ThesingleRFleadisaccompaniedbyagroundleadoneachside,whichformsacoplanarwave-guidetransmissionline.Inthismanner,aconnectorlessmodule is realized. In the secondapproach, the inter-connectionbetweenthemodulesandtheRF,DC,anddigitaldistributionboardcanbemadewithfuzzbuttons.These components are made of fine, stiff wire that isgold-platedandrandomlyformed, likeascouringpad,into a small rod shape.Diameters as small as 0.5mm(0.020in.)areavailablecommerciallyatlowunitcost.Whenconstrainedinholes inathincarrierplateandthen sandwiched between PCBs, fuzz buttons form aplanarinterconnectionwithouttheneedforsolder,con-ductive epoxy, or a plug-and-socket connection. Thisprovidesalow-cost–compliantconnectionwithrelaxedtolerancesinthreedimensionsforbiasvoltagesanddig-ital control signals. A current-carrying capacity up to5Aisreadilyachieved.MultiplefuzzbuttonshavealsobeenusedsuccessfullyforRFconnections.

The LCPA design concept features a minimumnumberofcomponentsandintegratedstructure,cool-ing, and alignment functions. Such highly integratedstructurescancreatesignificantinherentstiffness,allow-ing the unit to survive the standard shipboard shocktestwithoutadditionalstructuralelements.Fromacool-ingperspective,theLCPAdesignconceptisadaptableto either liquid- or air-cooled approaches. Shipboardactiveapertureantennastendtobeliquid-cooled,pri-marily driven by the need to maintain junction tem-peratures to support high reliability, and thus have averylowprobabilityofmaintenanceactionduringtheship’smissionwhileinanoperatingtemperaturerangeof–25°to+55°Cinasalt-ladenambientairenviron-ment.However,futurelandmobileapplications,whicharedrivenbydifferentmissionsandenvironments,willlikelybenefitfromair-cooling.

DEMONSTRATION T/R MODULES TodemonstratetheutilityofCOTS-basedmodules

forCEC, transmitand receivemodulesweredesignedandasmallnumberfabricatedandtested.Thedemon-stration modules (Fig. 4) used commercially availableMMICs.About12modulesofeachtypewerefabricatedandtestedatAPL.

ThetransmitmoduleusedaCOTSpoweramplifierMMIC,whichwas4mm2inareaandsupplied1.25WofRFpower at25°C.Thispower level is slightly lessthan the performance that would be required for theintended shipboard application. An MCOTS MMICpoweramplifierthatsuppliestherequiredoutputpower

23-dBgain

–3 dB –9 dB +18 dB

M/A-COMMAAM26100

+17 dB

1.26-Woutput power

Control

4-bit phase Driver Poweramplifier

–5 V +9 V @ 700 mA

Power and control

22-dBgain

North-GrummPHS2584

–9 dB

M/A-COMMAAM37000

+17 dB –3 dB

M/A-COMMAAM37000

+17 dB

3.4-dBnoise figure

Driver 4-bit phase LNA

Control–5 V +4 V @ 200 mA

Power and control

(a)

(c)

(b)

North-GrummPHS2584

M/A-COMMAAM28000

Figure 4. Transmit and receive modules fabricated at APL with COTS MMICs for the CEC LCPA concept evaluation array: (a) prototype transmit and receive modules and (b) transmit and (c) receive module block diagrams.



shouldoccupylessthan5mm2.BecauseanMCOTSorcustomdesigncouldbe10to15%moreefficientthanthe30%efficiencyoftheCOTSunit, theactualheatdissipationofthetransmitmodulecouldbelessinpro-duction units. The only suitable COTS phase-shifterchipidentifiedwasabroadband6-bitdesignthatoccu-pies26mm2inarea.Becausefewerbitsofphasecontrolarerequired,itisprojectedthatacustomdesigncouldbeassmallas4mm2,basedonscalingthesizeofcom-parableunitsthatoperateathigherfrequencies.Addi-tionally,a3-dBchipattenuatorwasplacednexttothephaseshifterintheRFpathtomitigatethelargevolt-agestandingwaveratioofthisdevice.Acustomphaseshifter would presumably be designed with a betterimpedance match, so the chip attenuator would notbeneededinproductionunits.Thustheconcepteval-uation modules are slightly larger and dissipate morepowerthantheprojectedproductionunits.

ThereceivemoduleusedaCOTSLNAandpostam-plifierchips,each2mm2inarea.Thisisaboutthemini-mumareaprojectedfortheseMMICs,eveniftheyarecustomdesigned forCEC.Thephaseshifter is identi-cal to that used in the transmit module. The receivedemonstration module was projected to have superiorperformancerelativetothecurrentCECT/Rmodule,basedontypicalvaluesfortheCOTSMMICchipsfrommanufacturers’datasheets.Thenoisefigureshouldbe1dBlower,thethird-orderinterceptpointattheinputshould be 5 dB higher, and the gain should be com-

board.Thisengagementalsolocatesthemoduleonthecoldplatepriortosecuringitwithshoulderscrews,whichare accommodated by slots in the package base. Thishousing provides a large surface area to conduct heatfromthepower-amplifierMMICchiptothecoldplate.Bothreceiveandtransmitmodulesusethesamehousing.Aproductionversionofthishousingcouldeliminatethescrew-mountingtabs(Fig.4)infavorofcompliantcon-ductiveepoxymountingtothecoldplate.Whilereduc-ing the weight of each module only slightly, it wouldhaveasignificantimpactonsystemweightbecauseofthelargenumberofmodulesineacharrayface.

About 12 modules of each type were assembledatAPLusing standardmicroelectronicprocessesandtechniques.Internaldetailsofthisassemblyareshownin Fig. 5. A multilayer ceramic substrate is mountedto the base of the package and surrounds a pedestalformed integral to the base. The MMIC chips aremountedon thispedestalwithconductiveepoxy (oreutectic solder in the case of the power amplifier).Theceramic substratecontains imbeddedwiringandcomponentmountingpads forbiasandcontrol func-tionsthatareuniquetoeachmoduletype.Thissub-stratewasfabricatedatAPLfromlow-temperatureco-firedceramicthatispatternedandroutedingreentapebeforebeingstackedandfiredunderpressuretoformanintegratedmultilayerceramicunit.ThetopoftheceramicsubstrateiseveninheighttothetopsurfaceoftheMMICchips,thusallowingdirectwirebonding

parable.Thedemonstrationreceivemoduledoesnotuseareceivepro-tector to shield the MMIC fromthe electromagnetic environment.Areceiveprotectorcouldbeimple-mented in the aperture multilayerboardorinthemodule.Thedem-onstrationreceivemodulehasmorethanenoughperformancemargintoaccommodate the insertion loss ofthereceiverprotectorandRFfilterinshipboardproductionunits.

Thehousingselectedforthedem-onstration modules is similar to acommercial unit used to house RFpowertransistors.KyoceraAmerica,Inc. modified its hermetic packageto APL requirements by placing aglasssealfeedthroughinthecoppertungsten base and providing eightribbonleadsthroughaceramicwallon one side. As described previ-ously, the center pin of the glassfeedthrough engages a pogo pin inthe cold plate to make a coaxialconnectiontotheradiatingelementthrough the aperture interconnect

Figure 5. Details of the CEC LCPA concept evaluation module designed and fabricated at APL.

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to the bias and control wiring on the substrate withminimalheightchangeorinterferencetothebondingtoolfromcomponentfeatures.Chip-to-chipwirebond-ingwasusedbetweenMMICchipsand fromMMICchips to chip capacitors mounted on the pedestal.Constant-lengthwirebonds3wereusedforallRFpathconnections. This has the effect of controlling theimpedanceateachinterconnection,whichleadstouni-formityinelectricallengthfrommoduletomodule.

Followingassembly,themodulesweretestedforRFfunctionalitybefore lidswerewelded inplace to formahermeticpackage.Ofthe12transmitmodulesfabri-cated,9passedthepre-sealfunctionaltest.Twoofthefailedmodulesweresubsequentlyreworkedandwentonto post-seal characterization. The remaining transmitmodulehadafailureintheceramicsubstrate.Eleven,or92%,ofthetransmitmodulesfabricatedwerecharacter-izedandincludedinthetotaldataset.Ofthe11receivemodules fabricated, 10 passed the pre-seal functionaltest.Afterrework,11werecharacterizedpost-seal.Onereceive module failed in characterization, leaving 10units, or 91%, to be included in the data set. Bothreceivemodulefailuressuggestthatreversebiasvoltagehadbeenappliedtothedigitalcontrolchip,leadingtospeculationofanintermittentshortbetweentheposi-tiveandnegativebiaslinesinthemodule.

Typicaltransmitmoduleperformanceatroomtem-perature (25°C) is shown in Fig. 6. The frequencyresponseforthefourmostsignificantbitsettingsofthephaseshifter,showninFigs.6band6c,indicatesappro-priate functionality of the phase shifter. The powersweep plot (Fig. 6a) indicates an output in excess of1.25 W (31 dBm) at the low end of the band. Thesecondandthirdharmonicoutputsareshownaswell.All11transmitmodulesprovidedameanoutputpowerof31dBmwitha1-deviationof0.25dBmat roomtemperaturewhenaveragedover the frequency range.Power-addedefficiencywas23.3%witha1-deviationof 1.9%under these same conditions.The10 receivemodulesprovidedameannoisefigureatroomtempera-tureof3dBandameangainof23.2dBwhenaveragedover the frequency band. It should be noted that thedatawerenot corrected for test fixture loss ormatch.ThusacoaxialinterfacetoanSMAconnector(whichusesapogopin)at theantennaportof themodule isincludedinthedata.

Figures7and8 showtheperformanceof themod-ules statistically. The root-mean-square (RMS) phaseandgainerrorsforallphasestatesforasampleoftwomodulesofeachtypeindicatephaseerrorsoflessthan6°andgainerrorsoflessthan0.5dBovermostofthemeasuredfrequencyband.Similarly,thestandarddevia-tion(1)ofgainandinsertionphaseovermostofthefrequency band measured for the entire population islessthan1.0dBand15°forthetransmitmodulesandlessthan0.5dBand14°forthereceivemodules.This

implies that no individual calibration constants needtobeappliedtothemodulesinanarraysetting.Suchuniformity betweenmodules is attributed to theuse oftheconstant-lengthwirebondtechniqueintheRFpath.

DEMONSTRATION ARRAYTodemonstratetheefficacyoftheLCPAdesigncon-

cept,anarraywasdesignedtofunctionallyreplicatethekeyfeaturesofanLCPAsubarrayLRUandthenfabri-catedandtested.Tominimizecosts,thearraywaskeptsmallandusedthe23modulesfabricatedatAPL.Thus,asubarraycontaininga18elementreceiveaperture

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Figure 7. Measured statistical performance of the transmit modules. (a) Photograph. (b) RMS phase and gain error for all phase states of two modules at room temperature and nominal bias. Mean and standard deviation of gain (c) and phase (d) for 11 modules at room temperature and nominal bias. (Gain and phase both at 0 state.)

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anda28elementtransmitaperturewasconstructed(Fig. 9). The receive aperture was populated byeight receive modules. In the transmit aperture, thecentral eight elements were populated with transmitmodules and theouter eightelementswerepopulatedwith module packages containing matched loads.Following the LCPA design concept outlined previ-ously, the demonstration array consists of an aperturemultilayerboardcontainingthepatchradiators,acoldplate,thetransmitandreceivemodules,andanRF,DC,anddigitaldistributionmultilayerboard.Tolimitcost,thedigitalcontrolboardwasmadetoplugintothedis-tributionboardasaconnectorizeddaughterboardratherthanusing the fuzzbutton interconnect.The receiverprotectors,isolators,andRFfiltersarenotincludedinthisdemonstrationarray.

Aperture BoardTheapertureboardintegratestheradiatingelements,

their feeds,andinterconnects intoasingle-piece lam-inated board attached to an aluminum backing plate.The radiatingelementsaremicrostrippatch radiators,withU-shapedslotsincavitiesformedwithplatedvias(Fig. 9a). The cavity implementation mitigates scanblindnesseffects thatcouldbecausedbysurfacewavemodes.Theinterconnectionsarerealizedwithpogopinsthatcontactthestriplinefeedcircuitsontheapertureboard.Thestriplinetransitionstomicrostrip,whichinturncouplestothepatchradiator.Theapertureboarduses0.5-ozcopper-cladDuroid3003fortheetchedfeedandpatchlayers.AthinlayerofKaptonisusedtopro-tecttheexposedsurface.

Cold PlateThecoldplate,whichservesasthestructuralback-

bone of the demonstration array, was designed to useforced-air cooling supplied by a shrouded muffin fan.Althoughthecoldplatecouldbemodifiedtouseanynumberofcoolingmethods,aircoolingwasusedtosim-plifytestinganddemonstratefeasibilitywithlow-powermodules. The cold plate provides a mounting surfaceandthermalpathfortheT/Rmodules,definesthespac-ing for each module through precise location of themounting holes, and ensures alignment with the RFfeedthroughs (pogo pins). The modules are attachedto the cold plate by shoulder screws passing throughthe module mounting ears. In a production antenna,themoduleswouldbebondedintopositioninsteadofscrew-fastened,thuseliminatingtheneedformountingears.TheRFfeedthroughsarelocatedinbossesinthecoldplatefinarea.Thefeedthroughsweredesignedtoreplicatetheconstructionofa50-semi-rigidcoaxialcable,withthepogopinservingasthecenterconductorheldinplacebyaTeflonsleeve.

Distribution BoardThedistributionofRFsignalsaswellasDCbiasand

digitalcontrolsignalsisaccomplishedwithamultilayerPCB(Fig.3).Thisboardmountstothecoldplatewitha spacerplateunder it andwith cutouts tofit aroundthemodules.ThePCBisorientedwiththedigitalandpowerdistributionlayersontopandtheRFbeamform-ing layers locatedagainst thecoldplate.Tomaintainproperimpedancematch,thePCBisfabricatedwithan

Figure 9. APL demonstration array: (a) front view showing the aperture board containing the trans-mit and receive microstrip patch radiating elements, and (b) back view showing the distribution board and T/R modules.

(a) (b)



exposedledgeintheRFsignaldistributionlayerateachcutout,allowingallmoduleconnectionstotakeplaceonthe imbeddedRFsignal layer.Thesemodule leadsconnecttotheRFbeamformer,theDCbiastraces,andthedata,clock,andstrobecontrolsignaltracesinthedistributionboard.ThespacerplateisusedtoelevatethePCBsuchthattheribbonconnectionstothemod-ulesareco-planar.Thedigitalcontrolsignalsemanatefromadigitalboardthatplugsintothethreeconnec-torsinthemiddleofthedistributionboardasadaugh-terboard.Separateconnectors,shownatthetopofFig.9b,providebiasvoltageconnectionfor9,4,and5V,andgroundreturnusingparalleledpinstohandlethecurrent.

The 10-layer distribution board contains a bottomRFgroundlayer,anRFtracelayer,andatopRFgroundlayer separatedby twoRFdielectric laminates.TheseRFlaminatessurroundacoppertracelayerandaresis-tivefilmlayer,whichaccommodatesstriplineWilkin-son power dividers and combiners with imbedded RFisolationresistors.Thepowerdividersarearranged ina16-wayequalamplitudeandphasepowerdivider toform the transmit beam. An 8-way equal amplitudeandphasepowercombinerisusedasthereceivebeam-former. The remaining seven copper layers are con-tainedonconventionalprintedcircuitlaminatemate-rial(FR4).Theselayersconsistofatopgroundlayer,apositivevoltageplanesplitbetween9and4Vonasinglecopperlayer,astrobebusslayer,anothergroundlayer,adatabusslayer,a5Vbuss,andaclockdistri-butionlayerlocatedabovetheupperRFgroundlayer.

PCBsaretypicallyfabricatedintheirentiretypriorto any routing of cutouts. For this board, the ledgethatisprovidedinsidethecutoutrequiredsomerout-ingbeforefinalbonding.Italsorequiredaccuratecon-trolofresinflowtopreventresinbleedoverthesoldertabs during final bonding. Additionally, because thefinished PCB would be unbalanced, there was someconcern about achieving reasonable flatness. Sincethisunconventionalarrangementmightbedifficulttomanufacture,thedesignwasfabricatedatAPLaswellas by two commercial vendors. The vendors wouldonlyacceptanorderonabest-effortbasis.However,allthreefabricationsweresuccessfulandachievedhighyields, demonstrating that this design is well withinthecapabilityofcurrentcommercialPCBfabricationprocesses.

Digital Control BoardTocontrolthedemonstrationarray,digitalcircuitry

was designed and fabricated to provide each modulewitha7-bitencodedphase-shiftvalueaswellasaDCpowercontrolbit.This8-bitword is input serially toeach module on a single data pin, with timing con-trolledbyanassociatedclockpin.Inaddition,astrobe

signalgatesthenewlyprogrammedvaluetotheDCbiasswitchorphase-shifterMMIC.Becausethereisanarrayofmodules,eachmoduleisaddressedandprogrammedinturnfromthedigitalbeamcontroller.Thecontrollerconsistsofa laptopcomputerthatcommunicateswithanarraycontrollerboardthroughaparallelprinterport.Adigitalcontrolboardoneachantennasubarraypanelacceptsthesignalsfromthearraycontrollerboardanddirects the8-bitdatavalue to theappropriatemodulebygatingtheclockonlytotheaddressedmodule.Thearray iscapableofacceptingdataata ratecompatiblewith CEC beam update rate requirements, which ismuch faster thancanbeprovidedby the laptopcom-puter.Therefore,thearraycontrolleractsasaratebufferbetween the laptop and the higher rate of the arrayitself. The high-speed programming of the array withthis controller can only occur in finite-length burstsowingtothemuchsloweraveragespeedofthelaptopcomputer.

A program in the laptop computer calculates thephase-shift values for each module based on therequestedbeam-pointingposition.Thearraycontrollerboardbuffersthesedataandconvertsthemfrompar-allel to serial format using programmed logic devicesoperatingata28.5-MHzclock rate.Thedata,clock,strobe,andmoduleaddresssignalsareoutputonfourRS-422 twisted-pair lines that can be up to 10 m inlength.Useofdifferentialdriversprovidesthemecha-nism to shift the referenceground level to5Vonthesubarrayboard,makingthelogiconthisboardsuit-able for directly driving the gate of depletion modetransistorswitchesontheMMICphaseshifterineachmodule. The digital control board directs data andstrobe signals in parallel to each module in a rowwhenthatrowisaddressed.Theclocksignalisdirectedseparately to each module only when that module isaddressed.Inthisway,digitalnoiseontheRFsignalisreduced.ThearraycontrollerboardwasfabricatedonaSchottkywirewrapboardandhousedwitha5-Vpowersupplyinaboxchassis.Thedigitalcontrolboardwasfabricatedusingmultilayerprintedcircuit technologyandplugsintoconnectorsonthesubarraydistributionboardasadaughterboard.

Measured PerformanceAfterinitialcheckoutinthelaboratory,thearraywas

movedtoanoutdoorrangewherereceiveandtransmitbeampatternswererecordedatseveralfrequenciesandbeam positions. As shown in Fig. 10a, the receivearray was populated with eight receive modules in asinglerow.A42transmitarraywasformedbypopu-latingthecentraleightpositionsofthetransmitarray.The outer four positions were populated with modulepackagescontaininginternalRFterminations.Figure10also shows azimuth patterns for both arrays at several



pointingangles.Acos()1.25scanlossresponseisplot-tedforcomparison.Becauseofthegainandphaseuni-formity of the modules, no corrections for individualmodules were made to the beam-pointing commands.Similarperformancewasmeasuredatotherfrequenciesintheband.

IMPACT TO THE NAVY AtthedirectionoftheCECProgramOffice,PMS

465,theLCPAconceptwastransitionedtotheCECDesignAgent,RaytheonCompany,inthefallof1998.RaytheoniscurrentlydevelopingafullyCEC-compli-antLCPAdesign,withinstallationonsurfacecombat-antsslatedtobeginin2003.AlthoughtheRaytheondesignand implementationdetailsdiffer, they followAPL’sLCPAconcept.Thecriticaldesignreviewstageiscomplete,andshipboardintegrationplanningactiv-ities are under way. Cost analyses project that theLCPAwillresultingreaterthan$0.5billionintotalownershipcostavoidancetotheNavy.AstheTech-nicalDirectionAgentforCEC,APLcontinuestobecloselyinvolvedinLCPAdevelopmentandshipboardintegrationefforts.

In addition to addressing current CEC shipboardantennaneeds,theLCPAconceptwasdevelopedwithaviewtowardfutureshipclassesandCECapplications.Forexample,theplanarconfiguration,highreliability,

Figure 10. Performance of the CEC LCPA concept evaluation array (a) as measured on the antenna range at APL. Electronic azimuth scanning out to 45° from broadside is shown for both the receive (b) and transmit (c) arrays.

and low life-cycle costs are conducive to applicationonfutureshipclassessuchastheDDX.Also,thesub-arrayarchitectureprovidesahighdegreeofmodularityand scalability that is amenable to implementing theLRUsinnewCECantennaapplications.Forexample,alower-cost,lower-weightcylindricalarrayimplementa-tionconcept,whichusesthesameLRUsastheplanarLCPA configuration, has been developed to addressships thatarebetter suited toapole-mast installationorpotentialCECland-basedmobileortower-mountedapplications.

SUMMARYThe LCPA concept was developed to address crit-

ical Navy needs for CEC antenna total ownershipcost reduction and flexible shipboard integration of asingleCECantennasystem.Figure11summarizesAPL’sLCPA development effort. The Laboratory combinedextensiveCECantennasystemengineeringknowledge,broadactivearrayantennatechnologyexpertise,insightinto commercial microwave and electronics manu-facturing techniques, and adisciplined focuson costtodevelop theLCPAconcept.A limitedamountofmodule and array hardware was designed and fabri-catedtocost-effectivelydemonstratethekeylow-costattributesoftheLCPAdesignconceptpriortorequir-ingaNavycommitmenttoafullLCPAdevelopment

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program.WorkingwiththeCECProgramOffice,PMS465,theLCPAconceptwasthentransitionedtotheCEC Design Agent, Raytheon Company, where adetailedLCPAdesigniscurrentlyunderdevelopment.APL remains fully engaged in supporting PMS 465in the development and ship integration of the pro-ductionLCPA.Raytheon’sLCPAdesignimplementa-tionisplannedforFleetintroductionin2003,withini-tialinstallationonDDG51classships.TheLCPAiscurrentlyprojectedtoprovidemorethan$0.5billiontotal ownership cost savings over the current CECshipboardactiveantenna.

Navy needs

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•Cost

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•Land-based antennas

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Figure 11. APL development effort for the LCPA.

REFERENCES 1 “TheCooperativeEngagementCapability,”Johns Hopkins APL Tech.

Dig.16(4),377–396(1995). 2 “MoreGrowthinCommunications,”Compound Semiconductor7(1),

47(Feb2001). 3 Lehtonen,S.J.,andMoore,C.R.,“ConstantLengthWirebonding

for Microwave Multichip Modules,” Int. J. Microcircuits Electron. Packag.23(1),110–117(2000).

ACKNOWLEDGMENTS:TheauthorswishtoacknowledgethecontributionsofthestaffofAPL,inparticularDavidVervenforhiseffortsinthedesignandfabricationofthedigitalcontrolschemeaswellasformoduletestanddataanal-ysis,JohnMarksfortheimplementationofthedistributionboardandallofthemechanicaldesigndetails,andJonLehtonenforworkingoutthedetailsofthemodulepackageaswellastheassemblyofthemodules.

THE AUTHORS

CRAIGR.MOOREisamemberofAPL’sPrincipalProfessionalStaffintheAirDefenseSystemsDepartment.HereceivedB.E.E.andM.S.degrees fromCornellUniversity in 1962 and 1964, respectively. Before joining APL in 1987, he wasemployedbytheNationalRadioAstronomyObservatory,theAustraliangovern-ment, and Allied Signal Corp. His work at APL has involved improvements tothehydrogenmaser,workonultrahighQcryogenicmicrowaveresonators,MMICdesignandtesting,anddesignanalysisofthenewairborneCECtransceiver.Heiscurrentlysupportingseveralactivephasedarrayprograms, includingCEC, intheareaoftransmit/receivemodulesandreceiver/excitersubsystems.Mr.Mooreisasenior member of the IEEE and has published more than 20 papers. He teachesMMICdesignfortheG.W.C.WhitingSchoolofEngineeringPart-TimePrograminEngineeringandAppliedScience.Hise-mailaddressiscraig.moore@jhuapl.edu.



MARKH.LUESSEisamemberoftheAPLSeniorProfessionalStaff intheAirDefenseSystemsDepartment.HereceivedaB.S.inmechanicalengineeringfromtheUniversityofMaryland.Mr.LuesseworkedatAAICorporationinHuntValley,Maryland,asadesignengineer,developingsimulationandtestequipment.Sincejoining APL in 1989, he has designed, analyzed, and managed various hardwaredevelopmentandfield test siteefforts.Mr.Luesse joinedADSD’sRadarSystemsDevelopment Group in 1996, working primarily on the mechanical design andpackagingoversightofactivephasedarrayradarandcommunicationsantennas.Hise-mailaddressismark.luesse@jhuapl.edu.

KENNETHW.O’HAVERisamemberofAPL’sPrincipalProfessionalStaffandAssistantSupervisoroftheAirDefenseSystemsDepartment’sRadarDevelopmentGroup. He received a B.S. in electrical engineering from Virginia PolytechnicInstitute in1981andanM.S. inelectricalengineering fromThe JohnsHopkinsUniversity in 1984. Mr. O’Haver joined APL in 1984 and has been engaged inthe development of phased array and active aperture antenna systems and tech-nologiesforshipboardradarapplicationsandshipboardandairbornecommunica-tions applications. He is the lead engineer at APL for antenna development fortheNavy’sCooperativeEngagementCapabilityProgramandistheNavyIntegratedProduct Team lead for SPY-3 radar array antenna equipment development. [email protected].

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