Numerical Analysis and Design of Antenna Systems for Micro/Nano Satellites

240 Pages·2013·20.12 MB·English

by  Rosati, Gabriele

Numerical Analysis and Design of Antenna Systems for
Micro/Nano Satellites
THÈSE NO 5680 (2013)
PRÉSENTÉE LE 22 MARS 2013
À LA FACULTÉ DES SCIENCES ET TECHNIQUES DE L'INGÉNIEUR
LABORATOIRE D'ÉLECTROMAGNÉTISME ET ACOUSTIQUE
PROGRAMME DOCTORAL EN GÉNIE ÉLECTRIQUE
ÉCOLE POLYTECHNIQUE FÉDÉRALE DE LAUSANNE
POUR L'OBTENTION DU GRADE DE DOCTEUR ÈS SCIENCES
PAR
Gabriele ROSATI
acceptée sur proposition du jury:
Dr S.-R. Cherkaoui, président du jury
Prof. J. R. Mosig, directeur de thèse
Prof. A. Freni, rapporteur
Prof. F. Rachidi-Haeri, rapporteur
Dr I. Stevanovic, rapporteur
Suisse
2013

[...] vincer potero dentro a me l’ardore
ch’i’ ebbi a divenir del mondo esperto
e de li vizi umani e del valore;
ma misi me per l’alto mare aperto
Dante, Commedia, Inferno, Canto XXVI

Abstract
Recent space research and activities have been characterized by a growing emphasis on the
development of small spacecrafts. Since the year 2000, more than 30 micro/nano satellites
were built and launched. Today, constellations of micro-satellites are an efficient alternative
to traditional platforms for short missions involving security and survey, imaging and data
acquisition or telecommunications. Typical functionalities like TT&C or inter-satellite
cross-link require multi-functional antenna systems for the concurrent generation of different
antenna modes; the extremely stringent accommodation requirements pose a significant
challenge as the integration of the antenna with the spacecraft can critically affect the
radiation performance, especially when the size of the satellite platform becomes comparable
with the wavelength.
The lack of established methodologies for the design of antenna systems for small satel-
lites, providingspecificradiation patterns, inspiredtheresearch performedinthisthesis work.
In the frame of the ESA project MAST, requiring the design of a typical antenna system
for small platform, we developed a specific design strategy, based on the use of platform-
independent antennas, which led to the implementation of the simulation software SatAF.
Targeting the accurate predictions of the radiation performance of large arrays of identical
elements, together with a competitive computational time, the simple 3D Array Theory was
integrated in SatAF with original implementations of the Method of Moments.
In view of dedicated applications to slot antennas, a novel, simplified slot excitation model
wasdeveloped,allowingtherealisticrepresentationofthephysicalfeedingmechanismwithout
the necessity of including the feeding structure in the simulation model.
The “Magic Distance Inspired” method, an original formulation of the Nystro¨m method for
the numerical approximation of Integral Equations, allowed the replacement of the time-
demanding computation of the four fold integrals, necessary in canonical MoM algorithms,
with point-to-point computations performedaccording to specialpoint grids. Together with a
significative reduction of computational time, the formulation offers a number of advantages,
like an efficient computation of the singular, quasi- and non-singular entries of the MoM ma-
trix with a single formulation, and thepossibility of extension to complex environment where,
for instance, potentials and MPIE encounter difficulties.
The development of SatAF-MDI as alternative to brute force full-wave software constitutes
the original contribution of this thesis.
Keywords: Micro-satellites, Slot antennas, Computational electromagnetics, Method of Mo-
ments, EFIE, MPIE, Nystro¨m method.
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Sintesi
La recente attivit`a di ricerca in ambito spaziale `e stata caratterizzata da una crescente enfasi
posta sullo sviluppo di micro-/nano-satelliti, con un totale di piu` di 30 missioni effettuate
dall’inizio del secolo. Costellazioni di microsatelliti rappresentano oggi una valida soluzione
in missioni di sicurezza, sorveglianza, acquisizione di dati o telecomunicazioni.
Funzionalita` quali TT&C o cross-link inter-satellitare richiedono sistemi multi-funzionali di
antenne per la generazione simultanea dei diversi modi di radiazione; gli stringenti requisiti
di alloggiamento costituscono inoltre una vera e propria sfida in quanto l’integrazione
dell’antenna con la navicella puo` compromettere severamente la radiazione.
L’attivit`a di ricerca compiuta in questa tesi `e stata ispirata dalla mancanza di ben affermate
metodologie di design di sistemi di antenne per micro-satelliti.
Nell’ambito del progetto ESA “MAST”, che richiedeva il progetto di un sistema di antenne
per micro-satelliti, abbiamo sviluppato una strategia basata sull’uso di antenne indipendenti
dalle caratteristiche della struttura circostante, che ha condotto all’implementazione del
software di simulazione SatAF. Mirando ad un’accurata previsione delle caratteristiche di
radiazione di array costituiti da un elevato numero di elementi identici fra loro, oltre che a un
competitivo tempo di calcolo, i semplici elementi di Teoria degli Array tridimensionale sono
stati integrati in SatAF insieme con un’originale implementazione del Metodo dei Momenti.
Nella prospettiva di un’applicazione orientata in particolare ad antenne ad apertura, `e stato
sviluppato un innovativo e semplificato modello per l’eccitazione della slot, che permette
una realistica rappresentazione del fenomeno fisico di accoppiamento senza la necessit`a di
includere nel modello di simulazione la struttura di alimentazione.
Il metodo “Magic Distance Inspired”, una originale formulazione del metodo di Nystro¨m
per la soluzione di Equazioni Integrali ha permesso di sostituire il calcolo degli integrali in
quattro dimensioni, necessari per gli algoritmi canonici del MoM, con calcoli punto-punto
effettuati sulla base di speciali griglie. Insieme a una significativa riduzione del tempo di
calcolo, la formulazione offre una serie di vantaggi quali un efficiente calcolo dei termini,
singolari, e non, del MoM con un’unica formulazione valida in ambienti complessi dove, ad
esempio, i potenziali e la formulazione MPIE entrano in crisi.
Lo sviluppo di SatAF-MDI come alternativa ai software full-wave costituisce il contributo
originale di questa tesi.
Parole chiave: Micro-satelliti, antenna ad apertura, metodi numerici per
l’elettromagnetismo, Metodo dei Momenti, EFIE, MPIE, metodo di Nystro¨m .
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Acknowledgements
First and foremost, to my thesis advisor Prof. Juan R. Mosig for his trust, inspiration
and invaluable support during these years. His true passion for electromagnetism was a
great motivation for this work and scientific discussions we shared were a unique experience.
Thank you Juan.
My appreciation goes to the committee members Prof. Angelo Freni, from University of
Florence, Prof. Farhad Rachidi from EPFL and Dr. Ivica Stevanovic from ABB Schweiz for
having accepted to examine this work and for all their useful remarks which contributed to
improve the value of this thesis; I would also like to thank Prof. Rachid Cherkaoui for charing
this Jury. My gratitude to Angelo, thank you for introducing me to electromagnetism and
guiding my studies during and after the university.
Thanks to all the permanent members of LEMA: Prof. Anja Skrivervik for her support
and professional advice, Michael der Zauberlehrling, l’enfant terrible, Herv´e, Julien, J.-F.
Zu¨rcher for his availability and professionalism during the measurements of the satellite
antenna system, David, our and in particular to Eulalia for running flawlessly the most
delicate matters.
Huge thanks to the LEMA guys. To Marco, my office mate and the best bike trainer,
with whom rooftops became bike trips: grazie Campione. To the Docs: Eden, for all
our philosophic conversations, you better than anyone else deserve the “Ph” in your title,
Roberto; always and forever there to lend a hand; Benji, le foie gras in Toulouse will never
be enough for us, Thanos, Francesco, Sergio, all the Acoustic group with whom I wish I
had spent more time together. To the Docs wannabes: Ioannis, always waiting for you
down the slopes but the most contagious laugh ever, Rafal my first ski teacher, David, Apo,
Marc, Jovanche, Nuno, Eduardo, Anton, Michele, Baptiste, my past and present office mates
Mohsen and Nuno: guys you really made this four years a great andunforgettable experience.
Special mention for the beautiful LEMA girls: Madda, Laleh, Ruzica, Gabriela and most
recently Elena and Maria for cheering up the atmosphere here at LEMA.
Thanks to the JAST team, Stefano Vaccaro, Ferdinando Tiezzi, Jos´e Padilla, Fr´ed´eric
Bongard and Carolina Vigan`o for the very nice collaboration during the project MAST and
the MILAS, MASSA, MAST-X proposals we prepared together.
Finally, the most grateful thanks to my family, who raised and guided me: without your
supportI would never have made it here. Thanks to my uncleand aunt, to my cousins Letizia
and Cristiano. To all of them is dedicated this thesis.
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