kamal sarabandi: bridging the divide of fundamental

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Whether acquiring data from the furthestboundaries of the solar system, assessingglobalwarming,seeing throughwalls,oras-sisting communication among city dwellers

or soldiers in the field, Prof. Kamal Sarabandi is stronglygrounded in thebasics. “The reasonwecandosuchvastareasofresearchisthatwearedoingtheresearchatthefundamentallevelconsid-eringvariousinteractionsofwaveandtheobjectsofinterest.”

Prof. Sarabandi received his training among thebest, here at Michigan. He now leads where heoncetrained,asdirectoroftheRadiationLabora-tory,apositionhehasheldsince2000.TheRAD-LABiscomposedofeightfaculty,4researchscien-tists,andnearly50graduatestudentswhoconductresearch inareasasdiverseasantennas,meta-materials, computational electromagetics, radiofrequency (RF) propagation, microwave circuits,remotesensing,andplasmaelectrodynamics.

Prof. Sarabandi and his research group explorenewavenuesofresearch,suchastheuseofmeta-materials, while they continue to expand knowl-edge inmicrowaveandmillimeter-wave radar re-motesensing—anareahehasworkedinformorethan twenty years. In recognition of his accom-plishments, he received the 2005 DistinguishedAchievement Award from the IEEE GeoscienceandRemoteSensingSociety.

ReachingintoSpacetoLearnMoreaboutEarth

Prof. Sarabandi has been interpreting data fromspaceformorethanadecade—relatingittoissuesofglobalwarming,andprovidingthedataforsci-entists doing environmental research. “We needtoprotectourplanetandunderstandwhatisreallyhappening,”statedKamal.

NASA plans to establish a base station on themoonby2020toaidcontinuedspaceexploration.Kamalisalreadyplanningtheinstrumentationthatwouldbeusedonthislunarbasestationtoobserveprocessesoccurringontheearththatwouldbeim-possibletodoanyotherway.Hepredictsitcouldbe possible to measure small relative motions oflandmasses, includingearthquakeactivity,whichcouldleadtoanabilitytopredictearthquakes.

Meanwhile, NASA probes are being sent to thefar reaches of the solar system—collecting data,and taking pictures, video, and radar images asthey go. Getting the informa-tion back is a challenge, andthe main stumbling block isthe antenna—Kamal’s spe-cialty.Thecostofanantennalarge enough to transmit in-formation efficiently is about $1B.Kamalhasbeenworkingon a new technology that willemplyalargearrayofsmallerantennas, thousandsof them,working together to create, ineffect, a very large aperture.Until there is a lunar base station, which wouldsimplify the phase calibration of these antennas,themoonwillbeusedasacalibrationtargetusingInSAR(InterferomatetricSatelliteApertureRadar)imagingtechniques.

Keeping earth science as an important activitywithinNASAisahighpriorityforKamal,whohasbeenrecentlyappointedtoanadvisorycommitteechargedwithplanningthefutureactivitiesofNASA.“Thereisreallynootheragencywiththeexpertisetodealwithallthecomponentsthatareneededforobservingearthasasystem, includingdesigninginstruments, launching satellites, and interpretinganddistributingdata,”hesaid.“Spaceexplorationneedstoincorporatecontinuedremotesensingoftheearth.”

KamalSarabandi,ProfessorandDirectoroftheRadiationLaboratory

KamalSarabandi:BridgingtheDivideofFundamentalScienceandTechnology

“We need to protect our planet and understand what is really happening.”

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RemoteSensingforSafetyandSecurity

Hereonearth,Prof.Sarabandihasdevelopedim-portanttoolsandmethodsintheareaofradarre-motesensing tostudycomplexsystemssuchascarbon cycle, which affects global warming, andsoilmoistureandsnow,whichcanrevealproblemsrelated tohydrology,ecology,andclimate.Radarremotesensingalsohasawidevarietyofapplica-tionsrelatedtosecurityandsafety.

Onenewly-fundedproject investigates theuseofradartopenetratethroughwallsandcreateamapof the interior tosee if therearepeopleorweap-onry inside. He is collaborating with Ohio StateUniversityandthecompanyScienceApplicationsInternational Corporation (SAIC) in this project.BasedinCalifornia,SAICrecentlyopenedanAnnArbor office for their Reconnaissance and Surveil-lanceOperation.

Kamalisalsoworkingonarelatedsystemthatcanscanacrowdanddeterminewhetherornotpeopleare concealing weapons. This will enable quick,broadcoverageofanarea.Suspiciousindividualsmaythenbepulledasideandaskedtostandinadevicethatwill“see”throughclothing,suchaswasrecentlyimplementedatthePhoenixairport.

Turning his attention to safety issues, Kamal isdeveloping a millimeter-wave radar system thatwillbemountedonhelicopterstomaptheterrainunderneath.Pilotsaresubjecttohighlydangerouslandingconditionswhenlandingineithersnowordusty/sandyregions.Itisalsoimpossibleforthemtoknowwhatliesbeneaththeimmediatesurface,suchasaditchorarock.Thenewtechnologywillenablepilotstoseethroughwhite-outorbrown-outconditions, and to know on what kind of surfacetheyarelanding.

Prof. Sarabandi explains that his research canreach into such a wide variety of areas becauseappliedelectromagneticsisahighlysuccessfuldis-ciplines with significant impact on a wide range of technologies.Withthewallpenetrationproject,forexample,oncehedeterminesthescienceofwhathappenstoawaveorsignalasitpenetratesawall,hewillundowhatthewalldidtothesignalandre-constructtheimage.

CommunicationthroughWavesandSensors

With satellites in space and cell phones on theearth,theU.S.populationiscomingtoexpectnearinstant communication. Losing a connection withsomeoneeven foramomentbecomesvery frus-trating.Thesituationbecomesdownrightdanger-ous for troops communicating in the field.

Prof. Sarabandi has analyzed wave propagationinanurbanenvironment for thepurposeofwire-lesscommunication.Hisresearch,whichhasbeencommercialized, enables planners to establishbasestationsthroughoutacitytoensurecoverageforanentirearea.Heisnowturninghisattentiontoprovidingouractive troopswith thesamecov-erage,evenwhentheyaresent tounfamiliar ter-ritories.

To gather information about these areas, Kamalis developing miniature low-power unattendedground sensors to measure a variety of environ-mentalvariables,suchasvibrationsfromvehiclesandsound,aswellastotransmitphotosoftheareaand other information derived from radar. Theseelectronictransceiversactasanetworkwitheachother, communicating informationbetweennodesuntiltheinformationissenttoasatellite,andulti-mately toabasestation.Thesesensorsareonlypossiblethroughtheintegrationofminiatureanten-nasdevelopedbyProf.Sarabandi.

Antennasthebottleneckandkey

“Wecanmakemicroelectronicsvery,verysmall,”explainsProf.Sarabandi,“butthebottleneckeven-tually becomes the antenna.” It is extremely difficult to make antennas smaller without greatly sacrific-ing theirperformance,yet thegrowingnumberofwireless applications for low-cost, power-efficient, andminiatureelectronicsmakesthisanimportantareaforcontinuedresearch.PerfectingantennasforavarietyofuseshasbeenamainstayofSarabandi’sresearch; he has five patents in the area of antennas, andanothersixinthepatentprocess.

WhenhewasapproachedbyProf.MichaelFlynn,a member of the Center for Wireless IntegratedMicrosystems,tocollaborateonaprojectcreatingminiatureenvironmentalsensors,Kamalcameupwithanovelsolutiontotheproblemofintegratinganon-chipantennawithawirelesstransceiveron

(a) Colossus reflec-torantennaswithhighradiatedpowerfordeep-spacecommuni-cationwillbereplacedwithalargephasedarray of small reflectors andmoderateradiatedpower.(b)TherelativemotionoftheEarthandMoonwilbeusedtoformSyntheticApertureRadar(SAR)imagesoftheMoon’ssurface.Theseimageswillbeemployedascalibrationtargetsforthephasedarray.

A0.3mm2Min-iaturizedX-BandOn-ChipSlotAntennain0.13mmCMOS

(a)

(b)

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aCMOSICwithRFcircuitry.Thebasisforhisso-lutionwasanadaptationoftheslotantenna.Thistiny silicon-compatible antenna is capable of be-ingmass-produced,andhaspotentialapplicationsin remote wireless environmental sensors, cellphones,andlaptops.Sarabandihasalreadybeentalkingwith Intel about using theantennadesignin wireless laptop computers. This breakthroughtechnologyhasbeenfeaturedinEE Times.

MetamaterialsforAntennas

The ability to shrink the size of an antenna whilemaintaining high efficiency is a tremendous chal-lenge,withhighdividends inpotential applications.About five years ago, Prof. Sarabandi began to con-sider the use of artificial materials, called metamateri-als,toachievethisresult.

Working in Prof. John Halloran’s in the MaterialsScienceDepartment,Prof.Sarabandiandhisgrouptookarathersimpleceramicmaterial,similartoacoffeemug,andusedceramicstereolithographytoconstructa3-Dmonolithicmillimeter-waveantennawith a sophisticated computer-generated pattern.Animportantcharacteristicofthismetamaterialisits property of having both artificial permeability (µ) andpermittivity(e), which presents significant po-tentialforadvancingRF/wirelessfront-ends.Kamalisabletocontroltheindexofrefractionindifferentareasof thismetamaterialandactuallyguide thewaveandmakeitdowhathewants.

Pictured to the right is the first Luneberg lens an-tennaconstructedmonolithicallyfromthisceramicmaterial. Potential consumer and military appli-cations includeuseonanaircraftoronamilitaryhumvee,so thatyour laptop,oryoursoldier,canbe in constant communication via satellite. Thishasalreadyresultedinseveralpatentdisclosures.Prof.Sarabandiisworkingtoreachthehighertera-herz range of wavelengths with this technology,whichwouldopenanentirelynewareaofresearcheffort.

Antennasizetendstobedictatedbythefrequencyofthewave;thelowerthefrequency,thelargertheantenna.However,itisnotalwaysfeasibletohaveanantennasize thatcorresponds to the requiredfrequency. For example,Army vehicles have ex-tensive communications requirements with lowfrequency devices, yet it is not safe to outfit these vehicles with large, highly visual antennas. Prof.Sarabandisolvedthisproblembyusingametama-terialknownasReactiveImpedanceSurface(RIS)permittivity substrate, which enables a significantly smaller antenna size on today’s and tomorrow’sArmyvehicles.ThisworkwasrecongnizedwithaBestPaperawardatthe25thArmyScienceConfer-encethispastNovember.

EducatingStudentstoLeadtheWay

Prof.Sarabandisupportsalargenumberofgradu-atestudentstohelphimconductresearchinawidevarietyofareas,someofwhichhavebeenoutlinedabove. “Our students are critical to the work wedohere,”statedKamal,“WeareveryfortunateatMichigantohavesuchhighqualityindividuals.”

Theexcellenceof theirwork,combinedwith theirfocus on areas of high national interest, has re-sulted inahighnumberofstudentpaperawardsatrecentconferences.KarlBrakoraisaPhDcan-didate who has helped advance Kamal’swork inmetamaterials.Alreadyaprizewinnerforapaperin theareaofceramicstereolithography,which isemployed in theLuneberg lensdescribedabove,Brakora recently had his work published in theIEEE Transactions on Antennas and Propagation.Hespentmuchofhistimeinthelabcreatingthesecompletely novel structures. “It’s really quite anaccomplishment,” said Brakora, who appreciatedProf. Sarabandi’s patience through the extensiveexperimentationstagethatgoesintofabricatingacompletelynewstructure.

Prof.Sarabandi’scommitmenttohisstudentswasrecognizedearlyinhiscareerwhenhereceivedaU-MHenryRusselAwardforexcellenceinteach-ingandscholarship.AmyBuerkle,aPhDstudentworking with Kamal on acoustic and electromag-neticwave interaction,appreciateshisdedicationandzeal.She recalled that, “atoneofourmeet-ings,hepresentedasketchofanewideaonthebackofanairlinenapkin.”Aswell as valuinghisdepthofknowledgeandcreativeapproachtosolv-ing problems, she stated, “he has demonstratedthe importance of being well-rounded and usingour ability as engineers to benefit society.”

Prof.SarabandiwantshisstudentstobegintobuildtheircareershereatMichigan,withastrongfoun-dationinthefundamentals.“AlloftheworkthatIdoisfedbylookingatthefundamental issueofhowwave interacts with other material,” stresses Ka-mal.“IwantmystudentstohaveasolidfoundationinordertomoveontonewareasoncetheyleaveMichigan.Withawideanddeepknowledgeofonefield, you can do anything you want.”

Embeddedcircuitmeta-materialanditseffectivepermittivityandperme-abilityasafunctionoffrequency.

Amillimeter-waveLuneberglensfabricatedmonolithicallyusingce-ramicstereolithography.