Design, fabrication and measurements of an S-band radar in an airborne platform

58 Pages·2014·6.5 MB·English

by  Gerard Ruiz Carregal

DESIGN,FABRICATIONANDMEASUREMENTSOFANS-BANDRADAR
INANAIRBORNEPLATFORM
AThesisPresented
by
GERARDRUIZCARREGAL
SubmittedtoUniversitatPolitècnicadeCatalunya
EscolaTècnicaSuperiord’EnginyeriadeTelecomunicaciódeBarcelona
inpartialfulfillmentoftherequirementsforthedegreeof
ENGINYERIADETELECOMUNICACIÓ
October2014
ElectricalandComputerEngineering
UniversityofMassachusettsAmherst
DESIGN,FABRICATIONANDMEASUREMENTSOFANS-BANDRADAR
INANAIRBORNEPLATFORM
AThesisPresented
by
GERARDRUIZCARREGAL
Approvedastostyleandcontentby:
PaulR.Siqueira,Professor
ElectricalandComputerEngineering
To my family
iii
ACKNOWLEDGEMENTS
This work would have been impossible to finish without the help and encouragement
ofmanypeople.
First,IwouldliketothankProfessorPaulSiqueira,myadvisor,forgivingmethechance
toworkonthisproject. Hisadviceandhelphavebeenreallyimportanttomakethishappen.
IwouldliketothankDustinforhisbrightideasandhishelpwhenbuildingthesystem
andtestingit. ThankstoKrzysztofbecause,withouthislessonsintheworkshopandhisadvice,
this radar would have never been tangible. I cannot forget the antennas’ guy, thanks Chen for
designingthem. ThanksSheilaforaccompanyingme,andtheradar,tothehangar. Andthank
you,KanandYang,foryourhelpinthedataprocessing.
Finally,abigthankstomyparents. MylittleadventureintheU.S.andthisthesiswould
haveneverhappenedwithouttheirunconditionalsupport,thankyouforeverything.
iv
ABSTRACT
TheneedofunderstandingEarth’scomplexprocessessuchasearthquakes, volcanoes,
ice dynamics or ecosystems requires the design of new instruments. NASA-ISRO Synthetic
ApertureRadar(NISAR)isthemissionplannedtoacquirethedatathatwillhelpthescientific
community to conduct this research. One of the instruments of the mission will be an S-band
radar.
This thesis describes the process of designing and building an S-band radar, hoping it
willhelp,inthefollowingyears,inthestudyofwhatkindofresultscanbeobtainedatthisfre-
quencyband. Thethesisreviewsalltheprocessneededtobuildtheradarandtestit,explaining
howitwasinstalledinanaircrafttotakemeasurementsandshowingthefirstresultsobtained.
v
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . v
LISTOFTABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
LISTOFFIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix
Chapter
1. IntroductionandMotivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 NISARmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2. RadarConcepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. SystemDesign . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Systemoverview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2 Powersupply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 Acquisitioncomputer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.4 Antennas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.5 Aircraftdoormodifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3.6 Radartransceiveroverview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.7 Up-converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.8 Down-converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.9 Signalcompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.10Receiverspecifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.11LocalOscillators(LO)stage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4. Buildingtheradar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.1 Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
4.2 Up-converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
4.3 Down-converter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4 Signalcompression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.5 Localoscillatorsstage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.6 Filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
5. Groundmeasurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.2 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6. Flightmeasurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6.1 Setup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
6.2 AcquisitionsoftwareandAIMS . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.3 Flightlinesandparameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.4 Initialresults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
vi
7. Contributionsandfuturework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
7.1 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
7.2 Futurework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
APPENDICES
A. NotationReference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
A.1 SymbolicNotation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
A.2 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
vii
LIST OF TABLES
Table Page
3.1. Power supply 18-pin circular connector for S-band radar and Ka-band airborne
radar. Thevoltagesmarkedwithanasterisk(*)arealwaysonduringstandby. Blank
entriesarenotconnected. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2. Frequencyspecificationsoftheradar.. . . . . . . . . . . . . . . . . . . . . . . . . . . 13
4.1. Componentsusedinbuildingtheup-converter. AllofthemhaveSMAconnectors. 20
4.2. Components used in building the down-converter. All of them have SMA con-
nectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.3. Components used in building the signal compression stage. All of them have
SMAconnectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.4. Components used in building the local oscillators stage. All of them have SMA
connectors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
6.1. Swathandrangeparameterswithalookangleof45º. . . . . . . . . . . . . . . . . . 39
6.2. TektronixAFG3252functiongeneratorflightconfiguration. . . . . . . . . . . . . . 41
viii
LIST OF FIGURES
Figure Page
2.1. Chirpslope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Blockdiagramoftheradarsystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Layoutofthemodifiedpowersupplyenclosure. . . . . . . . . . . . . . . . . . . . . . 8
3.3. Oneoftheantennasusedintheflightmeasurements. . . . . . . . . . . . . . . . . . . 10
3.4. Sketchofthedispositionoftheantennasinthedoorandpictureofthebuiltstruc-
ture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3.5. Blockdiagramofthetransceiveroftheradar. . . . . . . . . . . . . . . . . . . . . . . . 12
3.6. Spectrumwiththethreeimagefrequencybands,inred;thelocaloscillators,inblue;
andtheworkingbandoftheradar,ingreen. . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.7. Blockdiagramoftheup-converter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.8. Blockdiagramofthedown-converter. . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.9. Blockdiagramofthesignalcompressionstage. . . . . . . . . . . . . . . . . . . . . . . 15
3.10. Blockdiagramofthelocaloscilatorsstage.. . . . . . . . . . . . . . . . . . . . . . . . . 17
4.1. Topviewoftheradarenclosure.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.2. Sideviewoftheradarenclosure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.3. Up-converter. TheBBchirpisup-converted(travelsfromthelefttotheright)andit
isreadytobeamplifiedintheHPA. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4. Down-converter. The received signal in the antenna enters the LNA. The pulse is
down-converted(travelsfromthelefttotheright). Then,itisreadytogetcompressed. 21
4.5. Signal compression. The received chirp comes from the down-converter and it is
mixed with the BB chirp (before Tx) to get the beat frequency. After some filters and
amplifiers,itisreadytobesampled. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4.6. Localoscillatorswithsplittersandamplifiers. Thechirpissplittotheup-converter
andtothesignalcompressionstage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.7. L-bandsymmetricinterdigitalfilterdesignedandbuiltinthelaboratory. . . . . . . . 26
4.8. Measurement, madewithanetworkanalizer, ofthemagnitudeofS21ofthesym-
metricinterdigitalfilter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
ix
4.9. Groupdelayandphaseresponseofthesymmetricinterdigitalfiltermeasuredwith
anetworkanalizer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5.1. MeasurementfromLGRCroofatearlystagesoftheradar’sdevelopment. . . . . . . 29
5.2. Google earth view of the area scanned in the ground measurements from Mount
Sugarloaf.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.3. DeploymentofthesystematMountSugarloaf. . . . . . . . . . . . . . . . . . . . . . . 31
5.4. Typicalrippleinthespectrumofagroundmeasurement. CH0correspondstothe
antennainthemiddleoftheplate(closertothetransmitantenna)andCH1corresponds
totheantennasituatedfurtherfromthereceiver. . . . . . . . . . . . . . . . . . . . . . . . 32
5.5. Spectrum of a ground measurement. The response of the same pulse is plotted
for each channel. CH1 corresponds to the antenna which is situated farther from the
transmitter. Analuminumplatewasinstalledabovethetransmitantenna. . . . . . . . 33
5.6. Groundmeasurement.BignearfieldcouplinginCH0whichisclosertothetransmit
antenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.7. GroundmeasurementtakenfromMountSugarloaf.Aplatewasinstalledabovethe
transmitantenna. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
6.1. Setupinsidetheplane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
6.2. Plannedflightlines.Thegreenlinesindicatewherethelinesstart,theredlinestheir
end. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
6.3. Cross-trackgeometry. Thelookangleis45º. . . . . . . . . . . . . . . . . . . . . . . . . 39
6.4. Lines flown at two different altitudes: 600 m (blue) and 1200 m (cyan). The green
andredlinesarethestartingandendingpoints. . . . . . . . . . . . . . . . . . . . . . . . 40
6.5. Firstflightmeasurementsresults. Thealtitudeis600m. Thepolarizationisvertical.
Therangescalestartsat600mandendsat3750m. Thecross-rangevariesfrom10km
up to 13 km, depending on the image. The dynamic range for the reflectivity scale is
40-50dB,dependingontheimage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
x