A broadband FFT spectrometer for radio and millimeter astronomy

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1、Astronomy&Astrophysicsmanuscriptno.3568February5,2008(DOI:willbeinsertedbyhandlater)AbroadbandFFTspectrometerforradioandmillimeterastronomyA.O.Benz1,P.C.Grigis1,V.Hungerb¨uhler2,H.Meyer1,C.Monstein1,B.Stuber3,andD.Zardet41InstituteofAstronomy,ETH,CH-8092Zurich,Switzerl

2、and2AcqirisSA,1228Plan-les-Ouates,Switzerland3UniversityofAppliedSciencesSolothurn,Nordwestschweiz,Switzerland4ZMA,CenterforMicroelectronics,UniversityofAppliedSciencesAargau,Nordwestschweiz,SwitzerlandReceived/AcceptedAbstract.Thecorearchitecture,testsinthelabandfirstr

3、esultsofaFastFourierTransform(FFT)spectrometeraredescribed.Itisbasedonacommerciallyavailablefastdigitalsampler(AC240)withanon-boardFieldProgrammableGateArray(FPGA).Thespectrometerworkscontinuouslyandhasaremarkabletotalbandwidthof1GHz,resolvedinto16384channels.Thedatais

4、sampledwith8bits,yieldingadynamicrangeof48dB.AnAllantimeofmorethan2000sandanSFDRof37dBweremeasured.FirstlightobservationswiththeKOSMAtelescopeshowaperfectspectrumwithoutinternalorexternalspurioussignals.Keywords.Instrumentation:spectrographs–Techniques:spectroscopic1.I

5、ntroductioninasingledevice(e.g.Belgazemetal.2004).Digitalspectrom-etersbasedonFouriertransformationhavebeenrealizedwithSpectrometersfrommicrowavestosub-millimeterwavesareabandwidthofonly50MHzand1024channels(Stanko,Kleinusedtodetectandtomeasuremolecularlinesubiquitousin

6、&Kerp2005).starformingregions,planetaryandcometaryatmospheres.TheTherearemanyreasonswhydigitalsignalprocessingofhigherthefrequencies,thebroaderarethelines.Severalnewananalogsignalmaybepreferable.Mostimportantly,adigitalinstrumentsarecurrentlybeingputintooperation,sucha

7、sprogrammablesystemallowsflexibility.Thesystemcanbere-APEX,Nanten2andSOFIA,someofthemsuppliedbymul-configuredandimprovedbychangingtheprogram;itmaybetiplebeams.Multi-feedsingledishesforsub-millimeterwavestransportedatleastinparttonewhardware.Thestabilityandposeaseriousdem

8、andonthecapabilitytosurveysimultane-accuracyofadigitalsystemiswellcontrolled,oncethesig-ouslyasufficientlylargespectral