Hybrid Maritime Satellite Communication Antenna

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Hybrid Maritime Satellite Communication Antenna
Smith, Thomas Gunst
Publication date:
2013
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Citation (APA):
Smith, T. G. (2013). Hybrid Maritime Satellite Communication Antenna. Technical University of Denmark.

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Thomas Gunst Smith

Hybrid Maritime Satellite
Communication Antenna

PhD thesis, May 2013

Hybrid Maritime Satellite
Communication Antenna
Ph.D. Thesis
Thomas Smith
May 2013
The present work was carried out at DTU Elektro and Cobham Satcom in
partial fulfilment of the requirements for the Industrial Ph.D. degree from
the Technical University of Denmark.
Supervisors:
Ulrich Gothelf, Ph.D.
Niels Larsen, Ph.D.
Cobham Satcom
Olav Breinbjerg, Professor, Ph.D.
Oleksiy S. Kim, Associate Professor, Ph.D.
Electromagnetic Systems, DTU Elektro,
Technical University of Denmark

Abstract
Hybrid antennas for a maritime satellite communication terminal with simul-
taneous operation at L- and Ka-band have been investigated. The frequency
bandsofinterestare1,525.0 1,660.5MHz(RX+TX,RHCP),19.7 20.2(RX,
− −
LHCP) and 29.5 30.0GHz (TX, RHCP), which are all part of the Inmarsat
−
BGAN and Inmarsat GX services, respectively. The results of this study are
three antenna concepts, which demonstrates high performance at both L- and
Ka-band.
Acombinedsingle/dual-reflectorantennaisdesigned,whichpresentsafavourable
way of combining feed antennas for the diverse frequencies1. This antenna en-
ables the use of a conventional horn-fed dual-reflector for Ka-band, while a
backfire helical antenna is used to form a single-reflector antenna at L-band.
Simulations show excellent performance of the L-band backfire helical reflector
antenna, due to the utilization of the entire antenna aperture. The Ka-band
dual-reflector is inherently a high-gain and low-loss antenna, and investigations
show negligible impact of the L-band backfire helical antenna. Therfore, this
hybrid single/dual-reflector antenna presents a viable solution to the combined
L- and Ka-band antenna.
NovelhybridantennasthatuseFrequencySelectiveSurfaces(FSSs)areinves-
tigated,suchthatanL-bandantennacanbelocatedbehindandradiatethrough
the Ka-band antenna. A planar periodic FSS, that is reflecting at both 20 and
30GHzwhilebeingtransparentatL-band,isdesignedandanalyzednumerically.
TheFSSisincorporatedinaparabolicFSSreflectorantennathatisinvestigated
by full-wave analysis tools, and the antenna shows performance comparable to
conventionalreflectorantennaswithinitsfrequencybandofoperation. Aplanar
prototype FSS is manufactured and measured with particular attention to the
impact on the performance of an L-band antenna radiating through the FSS.
From these investigations, it is concluded that the FSS antenna concept is well
suited for hybrid L- and Ka-band operation.
1Patentpending,PCT/EP2013/050259.
i
ii Abstract
AprintedreflectarrayantennawithFSSground-planeisdemonstrated. The
reflectarrayproducesacollimatedbeamasacurvedreflector,butitsplanarpro-
fileenablesconventionalmanufacturingtechniquesusedforprintedcircuitboard
fabrication. For this purpose, a new type of reflectarray element, the concentric
dual split-loop element, is devised and investigated. This compact element fa-
cilitates phase-adjustment at 20 and 30GHz simultaneously, which is exploited
by a developed iterative design procedure. A numerical code is implemented
tosynthesizeandanalyzereflectarrays, andtwoprototypereflectarrayantennas
are fabricated - the first with a conventional solid ground-plane and the second
with an FSS ground-plane. The radiation patterns of the prototype reflectarray
antennasaremeasuredattheDTU-ESASphericalNear-FieldAntennaTestFa-
cility,aswellastheL-bandtransparencyoftheFSS-backedreflectarrayantenna,
andtheresultsdemonstratesthehighperformanceofthisnovelshared-aperture
antenna.
Resume´
Inærværendeafhandlingbeskrivesstudietafhybridantennertilenmaritimsatel-
litkommunikationsterminalmedsamtidiganvendelseiL-ogKa-b˚and. Despeci-
fikkefrekvensb˚ander1.525,0 1,660.5MHz(RX+TX,RHCP),19,7 20,2(RX,
− −
LHCP) og 29,5 30,0GHz (TX, RHCP), som alle er del af Inmarsat BGAN-
−
samt Inmarsat GX-systemet. Resultaterne af dette studie er tre antennekon-
cepter, der viser høj ydelse ved b˚ade L- og Ka-b˚and.
En kombineret enkelt/dobbelt-reflektorantenne udvikles, hvor der demon-
streres en fordelagtig m˚ade at kombinere fødeantenner til adskilte frekvenser2.
Denneantennemuliggørbrugafenkonventionelhorn-fødetdobbelt-reflektorantenne
vedKa-b˚and,mensenbagudstr˚alendehelixantenneanvendesienenkelt-reflektorantenne
vedL-b˚and. SimuleringerviserfortrineligydelsefordenL-b˚andsbagudstr˚alende
helixantenne-fødteenkeltreflektor,daheleantenneaperturenudnyttes. Ka-b˚ands
dobbelt-reflektorantennen er naturligt en høj-forstærkning og lav-tabs antenne,
og undersøgelser viser begrænset indflydelse af den L-b˚ands bagudstr˚alende he-
lixantenne. Derved udgør denne kombinerede enkelt/dobbelt-reflektorantenne
et lovende løsningsforslag til en hybrid L- og Ka-b˚ands antenne.
Nye hybrid-antenner der anvender frekvensselektive flader (FSSer) udvikles
s˚aledes, at en L-b˚ands antenne kan placeres bagved og transmittere igennem en
Ka-b˚ands antenne. En plan periodisk FSS, der virker reflekterende ved b˚ade 20
og 30GHz, mens den er gennemsigtig ved L-b˚and, designes og analyseres nu-
merisk. FSSen anvendes i en paraboloide-formet FSS-reflektorantenne, der un-
dersøges ved brug af integralligningsmetoder, og antennen fremviser ydelse, der
ersammenligneligmedkonventionellereflektorantenner. EnplanFSS-prototype
fremstillesogm˚alesmedsærligthenblikp˚ap˚avirkningenafenL-b˚andsantenne,
der str˚aler gennem FSSen. Af disse undersøgelser konkluderes det, at FSS-
antennekonceptet er velegnet til en hybrid L- og Ka-b˚ands antenne.
En trykt reflectarray-antenne med FSS-jordplan demonstreres. Reflectar-
rayet frembringer en kollimeret str˚ale som en krum reflektor, men dets plane
2Afventerpatent,PCT/EP2013/0502259.
iii
iv Resum´e
profil tillader almindelige produktionsmetoder der anvendes til fremstilling af
printplader. Til dette form˚al udvikles og undersøges en ny type reflectarray-
element; det koncentriske dobbelt split-ring element. Dette kompakte element
muliggør samtidig fase-justering ved 20 og 30GHz, hvilket udnyttes i en it-
erativ designproces. En numerisk kode implementeres til at syntetisere samt
analysere reflectarrays, og to prototyper af disse reflectarray-antenner frem-
stilles - den første med almindeligt jordplan og den andet med et FSS jord-
plan. Udstr˚alingsdiagrammer af de to prototype reflectarray-antenner m˚ales i
det radiodøde rum ved DTU-ESA Spherical Near-Field Antenna Test Facility,
ogligeledesm˚alesL-b˚andsgennemsigtighedenafreflectarray-antennenmedFSS
jordplan. Resultaterne fremviser høj ydelse af denne nytænkte aperturdelte an-
tenne.
Preface
The work presented in this thesis was carried out at Cobham Satcom3 and
the Electromagnetic Systems Group, Technical University of Denmark (DTU),
and was conducted from April 2010 to March 2013. The study was financed
by Cobham Satcom with support from the Industrial PhD Programme of the
Danish Ministry of Science, Innovation and Higher Education, while prototypes
and measurements were provided by DTU.
During the study, I have received guidance and support from a number of
people to whom I would like to extend my gratitude. Firstly, I thank my super-
visors Ulrich Gothelf and Niels Larsen (Cobham Satcom), and Olav Breinbjerg
andOleksiy S.Kim(DTU). Theircontinuing inspirationandguidance has been
invaluable to the outcome of this study. Min Zhou is thanked for the countless
hours of conversation, for proofreading this thesis, and for sharing his expertise
within reflectarrays. Martin Nielsen, Jan Mortensen and Frank Persson are all
acknowledged for their assitance in practical challenges, and for providing high-
precision mounts and support structures for the prototype antennas. Sergey
Pivnenkoisalsothankedforsharinghisexpertizewithinantennameasurements,
and for conducting these with state-of-the-art accuracy. At Cobham Satcom I
have had numerous technical discussions with colleagues in the Antenna R&D
division for which I am grateful, and I would particularly like to thank Morten
HagensenandJohanGranholmfortheirdirectandindirectcontributionstothis
project.
Finally, I extend my humble gratitude to my friends and family, for their
constant love and support throughout my studies.
Thomas Smith, May 2013
3FormerlyThrane&ThraneA/S.
v