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Design of equal division microwave power dividersStrydom, M. L. 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Equal division microwave power dividers are investigated in this study. A wideband
Wilkinson power divider and a wideband directional coupler with a centre frequency of
10 GHz were built. The design of the directional coupler is scaled, such that it can be used
between 18 and 40 GHz. The details of the electromagnetic analyses of these structures
are discussed and physical implementation issues are investigated.
In a complementary study to the design of planar microwave dividers, the FDTD computational
method was implemented and used to analyse the Wilkinson divider and the 18
to 40 GHz directional coupler.
Results are compared to those obtained from commercial numerical method packages and
in the case of the Wilkinson divider, to measured results.
Suggestions are made for improvements in the implementation of the directional coupler
and methods for a more efficient FDTD implementation are discussed. / AFRIKAANSE OPSOMMING: Mikrogolf drywings verdelers wat gelyk verdeel, word in hierdie studie ondersoek. ’n
Wyeband Wilkinson verdeler en wyeband gerigte koppelaar met ’n senter frekwensie van
10 GHz is gebou. Die onwerp van die gerigte koppelaar is ook geskaleer sodat die ontwerp
gebruik kan word tussen 18 en 40 GHz. Die details van die elektromagnetiese analise van
hierdie strukture word bespreek en kwessies rondom die implementering van die strukture
word ondersoek.
In ’n komplementere studie, is die Eindige Verskil Tyd Gebied numeriese metode (Engels:
FDTD) geimplimenteer en gebruik om die Wilkinson en die 18 tot 40 GHz gerigte
koppelaar te analiseer.
Resultate word vergelyk met resultate verkry met numeriesie metodes geimplimenteer
in kommersiele pakkette, en in die geval van die Wilkinson verdeler, ook met gemete
resultate.
Aanbevelings word verder gemaak vir verbeterings in die implementering van die gerigte
koppelaar asook metodes om ’n meer effektiewe FDTD kode te implementeer.
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FSK modem modules for SDR using different linux API'sKhaile, Patrick 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The purpose of this thesis is to implement the Frequency Shift Keying (FSK) modem
modules for the Software Defined Radio (SDR), using different Linux sound Application
Programming Interfaces (API's).
The FSK modulation scheme, uses coherent detection with matched filters.
The modules are implemented using the Linux operating system and the programming
language used is C/C++. Simulation is performed first and then followed by implementation
in real-time, using APIs.
The APIs used are Open Sound System (OSS), Advanced Linux Sound Architecture
(ALSA), Jack Audio Connection Kit (JACK) and PortAudio (PA).
In real-time two computers are used, one acting as the modulator and the other as the
demodulator. The two sound cards are connected by an audio cable.
Results obtained using OSS, ALSA and JACK are satisfactory.
Recommendations are subsequently made for the suitable API(s). Both ALSA and JACK
are the best APIs for the implementation. / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is om modules vir 'n frekwensieskuif-sleuteling (FSK) modem
vir 'n Sagteware-gedefinieerde Radio (SDR) te implementeer, deur gebruik te maak van
verskillende Linux klankargitekture (API's). Die FSK modulasieskema gebruik koherente
deteksie met aangepaste filters.
Die modules is geïmplementeer met behulp van die Linux bedryfstelsel en CjC++ is
gebruik as programmeringstaal. Simulasies is eers gedoen, gevolg deur 'n reële-tyd implementasie.
Die klankargitekture wat gebruik is, is Open Sound System (OSS), Advanced
Linux Sound Architecture (ALSA), Jack Audio Connection Kit (JACK) en PortAudio
(PA).
Twee rekenaars is gebruik vir die reële-tyd stelsel, waar een as die modulator optree en
die ander een as die demodulator. Die twee klankkaarte is verbind deur 'n klankkabel.
Bevredigende resultate is verkry met behulp van OSS, ALSA en JACK. Aanbevelings is
gevolglik gemaak vir toepaslike API's. Beide ALSA en JACK is die geskikste API's vir
die implementasie.
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Analysis and performance of antenna balunsKock, Lotter 03 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2005. / ENGLIAH ABSTRACT: Data transmission plays a cardinal role in today's society. The key element of such a system
is the antenna which is the interface between the air and the electronics. To operate
optimally, many antennas require baluns as an interface between the electronics and the
antenna. This thesis presents the problem definition, analysis and performance
characterization of baluns. Examples of existing baluns are designed, computed and
measured. A comparison is made between the analyzed baluns' results and recommendations
are made. / AFRIKAANSE OPSOMMING: Data transmissie is van kardinale belang in vandag se samelewing. Antennas is die voegvlak
tussen die lug en die elektronika en vorm dus die basis van die sisteme. Vir baie antennas
word 'n balun, wat die elektronika aan die antenna koppel, benodig om optimaal te
funktioneer. Die tesis omskryf die probleemstelling, analiese en 'n prestasie maatstaf vir
baluns. Prakties word daar gekyk na huidige baluns se ontwerp, simulasie, en metings. Die
resultate word krities vergelyk en aanbevelings word gemaak.
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The design and implementation of microwave receiver front end componentsNetshifhire, Vhudilangi Patrick 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Different types of RF and Microwave receiver systems architectures are investigated. The
superheterodyne receiver characteristics are studied qualitatively. A three components system
(LNA, Mixer and VeO) is selected and the components are first measured individually, and then
measured as a single system. A mono filar axial mode helix antenna is designed, simulated using
FEKO and constructed. A narrow band interdigital bandpass filter is designed using the
capacitance network and its transformation, and it is simulated using two different simulation
packages, eST Microwave Studio and AWR Microwave Office. Two filter prototypes are
fabricated using cylindrical rods. An open circuited microstrip resonator oscillator is designed
and implemented through the negative resistance method. Its performance is verified using the
harmonic balance simulator in AWR MWO. A single balanced mixer is designed and
implemented using 1800 hybrid junction (rat-race) and it is also fabricated using microstrip
transmission line technology. All designed components performed well in comparison to their
predicted performance. The LNA and three of the designed components (Filter, Oscillator and a
Mixer) are connected together and characterized as a single four block system. The system
performed well except for the IF signal which shift to a lower frequency due to oscillator load pulling. / AFRIKAANSE OPSOMMING: Die argitektuur van verskeie RF en Mikrogolf ontvanger stelsels word ondersoek. Die
"superheterodyne" ontvanger eienskappe is kwalitatief bestudeer. 'n Stelsel wat uit drie
komponente bestaan (LNA, Menger en VeO) is bestudeer. Die individuele komponente is eers
gemeet en daarna die stelsel as 'n eenheid. 'n "Mono filar" aksiale modus heliks antenna is
ontwerp, gesimuleer met FEKO en gebou. Verder is 'n nouband inter-digitale banddeurlaat filter
ontwerp met behulp van die kapasitiewe network metode en sy transformasie. Hierdie ontwerp is
gesimuleer deur van twee verskillende sagteware pakette gebruik te maak, naamlik eST
Microwave Studio en AWR Microwave Office. Twee filter prototiepes is gebou met silindriese
stafies. 'n Oopgeslote mikrostrook ossilator is ontwerp en geimplementeer deur negatiewe
weerstand te gebruik. Die stelsel se prestasie is bevestig deur gebruik te maak van 'n harmoniese
balans simulator in AWR MWO. Verder is 'n enkelbalans menger ontwerp en geimplimenteer
via 'n 1800 hibriede verbinding ("rat-race"). Hierdie menger is gebou met mikrostrook
transmisielyn. Al die ontwerpte komponente werk goed in vergelyking met die voorspelde
resultate. Die LNA, filter, ossilator en menger word gekoppel en gekarakteriseer as 'n vier blok
stelsel. Die stelsel werk goed behalwe vir 'n skuif in die IF-sein by laer frekwensies a.g.v. belasting.
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Harmonic mixer analysis and designVan der Merwe, Marius 03 1900 (has links)
Thesis (MScEng) -- Stellenbosch University, 2002. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: Harmonic mixers are capable of extended frequency operation by mixing with a harmonic of the
LO (local oscillator) signal, eliminating the need for a high frequency, high power LO. Their
output spectra also have certain characteristics that make them ideal for a variety of applications.
The operation of the harmonic mixer is investigated, and the mixer is analyzed using an
extension of the classic mixer theory. The synthesis of harmonic mixers is also investigated, and
a design procedure is proposed for the design and realization of a variety of harmonic mixers.
This design procedure is evaluated with the design and realization of two harmonic mixers, one
in X-band and the other in S-band. Measurements suggest that the procedure is successful for the
specific applications. / AFRIKAANSE OPSOMMING: Harmoniese mengers kan by hoer frekwensies gebruik word as gewone mengers deurdat hulle
gebruik maak van ‘n harmoniek van die LO. ‘n Hoe-frekwensie, hoe-drywing LO word dus nie
benodig nie. Die mengers se uittreespektra het ook ‘n aantal karakteristieke wat hulle goeie
kandidate maak vir ‘n verskeidenheid van toepassings. Die werking van die harmoniese menger
word ondersoek deur uit te brei op die klassieke menger-teorie. Die ontwerp van die harmoniese
menger word vervolgens ondersoek, waama ‘n ontwerpsprosedure voorgestel word vir die
ontwerp van ‘n verskeidenheid van harmoniese mengers. Hierdie prosedure word getoets met die
ontwerp en realisering van twee harmoniese mengers, een in X-band en die ander in S-band.
Vanuit die metings is dit duidelik dat die ontwerpsprosedure geslaagd is vir die spesifieke geval.
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Microwave dielectric heating through interference modulation with narrow band high power sourcesMeier, Ingolf 12 1900 (has links)
Thesis (PhD)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: One of the most difficult problems in microwave dielectric heating is the generation
and control of field and heating patterns. A technique allowing the synthesis of
different, pre-determinable heating patterns by interference modulation is proposed.
The proposed concept may be described by the term 'interference modulation'.
Interference modulation is a technique which enables particular patterns, called
features, to be obtained by signals from several sources interfering with each other.
The relative phases of the signals are modulated, by which process known features
may be selected. Weights are assigned to these features, which may be combined
over time to form a new heating pattern. Phase changes may then be used to switch
to specific, known features, with weights which will determine the contribution of
each feature to the desired overall pattern.
In the practical implementation described, magnetron tubes are the sources. Each
of these narrow-band high-power sources was injection locked to a low power
control signal. The control signals are derived from a reference source and their
phase is set to select a corresponding feature.
Calculation and measurement showed that reliable locking occurs with a control
signal power of at least 3% of the magnetron's emitted power.
Measurements of patterns were carried out with materials formed into sheets and
blocks. Some were chemically prepared to reveal the overall heating pattern. The
observed patters, simulations and field measurements concur, thus validating the
concept and operation of the proposed topology. / AFRIKAANSE OPSOMMING: Een van die moeilikste probleme in mikrogolf diëlektriese verhitting is die opwekking
en beheer van veld- en verhittingspatrone. 'n Tegniek wat voorsiening maak vir die
sintese van verskillende, voorafbepaalde verhittingspatrone deur interferensie word
hier voorgestel.
Die voorgestelde beginsel kan beskryf word deur die term "interferensie modulasie".
Interferensie modulasie is 'n tegniek wat spesifieke patrone, genoem kenmerke,
moontlik maak deur seine van verskillende bronne met mekaar te laat interfereer.
Bekende kenmerke kan geselekteer word deur die relatiewe fases van die seine te
moduleer. Gewigte word aan hierdie kenmerke toegeken wat oor tyd gekombineer
kan word om nuwe verhittingspatrone te vorm. Faseveranderings kan dan gebruik
word om na 'n spesifieke, bekende kenmerk te skakel met gewigte wat die bydrae
van elke kenmerk van die verlangde algehele patroon bepaal.
Magnetrons word gebruik as bronne in die praktiese implimentering wat beskryf word.
Elkeen van hierdie nouband, hoë drywing bronne is injeksie-gesluit met 'n lae
drywing beheersein. Die beheerseine is afgekoppel van 'n verwysingsbron en hul
fases is gestelom 'n ooreenstemmende kenmerk te verkry.
Berekening en meting toon dat betroubare sluiting voorkom wanneer die beheersein
ten minste 3% van die magnetron se uittree-drywing is. Metings van patrone is
gemaak met materiale wat in lae en blokke gevorm is. Sommiges is met chemikalië
voorberei sodat die algehele verhittingspatroon gesien kan word. Die
waargeneemde patrone, simulasies en veldmetings stem goed ooreen en bevestig
die beginsel en werking van die voorgestelde topologie.
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An image compression system for LEO satellitesKriegler, Eduard 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Data volumes produced by the next generation of earth observation sensors have increased
greatly in recent years. Sensors are generating more data than can be easily stored
onboard satellites and transmitted to the ground-stations.
There are two strategies for solving this problem. The first is to process all images
onboard the satellite, and only extract the useful or valuable information. The second is
to use a compression algorithm to reduce the data volume.
This thesis looks at both strategies and then focusses on an evaluation of the Embedded
Zerotree Wavelet (EZW) algorithm, a wavelet-based lossy image compression algorithm,
as a solution to reduce the data volumes. Possible hardware implementation strategies
for this algorithm are also explored. Finally, a suggested implementation of the EZW
algorithm is compared with the FlexWave-II system and with JPEG2000. / AFRIKAANSE OPSOMMING: Die data volumes wat deur die nuwe generasie van aardobservasiesensore geproduseer
word, het dramaties vergroot in die laaste paar jaar. Daar word nou meer data geproduseer
as wat aanboord van die satelliet gestoor kan word en meer as wat in die beperkte
kommunikasietyd aan die grondstasie gestuur kan word.
Daar is twee strategiee om hierdie probleem aan te spreek. Eerstens kan beelde aanboord
die satelliet verwerk word om die belangrikste of waardevolste inligting uit te haal en
die res van die data word dan geskrap. Die alternatief is om 'n beeldkompressie-algoritme
te gebruik om die data te verminder.
Hierdie tesis ondersoek hierdie strategieë en fokus dan op 'n evaluasie van die "Embedded
Zerotree Wavelet" -algoritme. Die EZW-algoritme is 'n verlieserige, golfie-gebaseerde
beeldkompressie-algoritme. Moontlike hardeware-implementeringsopsies word ondersoek
en die resultate van een voorgestelde opsie word vergelyk met die FlexWave-II stelsel
asook die nuwe JPEG2000-standaard.
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An object detection approach for cluttered imagesKok, R. 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: We investigate object detection against cluttered backgrounds, based on the MINACE
(Minimum Noise and Correlation Energy) filter. Application of the filter is followed
by a suitable segmentation algorithm, and the standard techniques of global and local
thresholding are compared to watershed-based segmentation. The aim of this approach is
to provide a custom region-based object detection algorithm with a concise set of regions
of interest.
Two industrial case studies are examined: diamond detection in X-ray images, and the
reading of a dynamic, and ink stamped, 2D barcode on packaging clutter. We demonstrate
the robustness of our approach on these two diverse applications, and develop a complete
algorithmic prototype for an automatic stamped code reader. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die herkenning van voorwerpe teen onduidelike agtergronde. Ons
benadering maak staat op die MINACE (" Minimum Noise and Correlation Energy") korrelasiefilter.
Die filter word aangewend saam met 'n gepaste segmenteringsalgoritme, en
die standaard tegnieke van globale en lokale drumpelingsalgoritmes word vergelyk met 'n
waterskeidingsgebaseerde segmenteringsalgoritme. Die doel van hierdie deteksiebenadering
is om 'n klein stel moontlike voorwerpe te kan verskaf aan enige klassifikasie-algoritme
wat fokus op die voorwerpe self.
Twee industriële toepassings word ondersoek: die opsporing van diamante in X-straal
beelde, en die lees van 'n dinamiese, inkgedrukte, 2D balkieskode op verpakkingsmateriaal.
Ons demonstreer die robuustheid van ons benadering met hierdie twee uiteenlopende
voorbeelde, en ontwikkel 'n volledige algoritmiese prototipe vir 'n outomatiese
stempelkode leser.
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Precision propagation and orbit decay predication of low earth orbit satellitesOpperman, B. D. L. 12 1900 (has links)
Thesis (MScEng)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: This study investigates the theory of precision satellite orbit propagation and satellite
lifetime prediction and lead to the development of two necessary software tools for
analysis in these fields. Precision propagation was achieved through the implementation
of Cowell's method of special perturbations, considering perturbations due to a 70x70
asymmetrical gravity field, atmospheric drag, Luni-Solar attraction and Solar radiation
pressure. The satellite's perturbed equations of motion were integrated utilizing a seveneighth
order Runge-Kutta-Fehlberg numerical integration procedure, limiting error
propagation by employing adaptive step size control. The MSlS-90 atmospheric density
model, providing for diurnal and semi-annual variations, was employed to determine
atmospheric density. Care was taken in the precision modelling of the motion of the
12000 equator and equinox. Propagation results for this test case proved to be superior to
the SGP4 propagator and a commercial package.
The long-term effects of Earth oblateness and atmospheric drag on a satellite's orbital
elements were investigated and applied to the orbit decay prediction problem. Orbit
decay was predicted by integrating the rates of change of the orbital elements due to Earth
oblateness and atmospheric drag. A semi-analytical technique involving Runge-Kutta
and Gauss-Legendre quadrature was employed in the solution process. Relevant software
was developed to implement the decay theory. Optimum drag coefficients, estimated
from drag analysis using precision propagation, were used in decay prediction. Two test
cases of observed decayed satellites were used to evaluate the theory. Results for both
test cases indicated that the theory fitted observational data well within acceptable limits. / AFRIKAANSE OPSOMMING: 'n Ondersoek is gedoen oor die teorie van presiesie satelliet-wentelbaan vooruitskatting
en satelliet-wentelbaanleeftyd afskatting en het gelei tot die ontwikkeling van twee
analiseprogramme vir gebruik in hierdie vakgebiede. Presiesie vooruitskatting is bereik
deur die gebruik van Cowell se metode van spesiale perturbasies, wat die invloed van 'n
nie-simmetriese 70x070 gravitasieveld, atmosferiese sleur, Son-Maan aantrekkingskragte
en druk van sonradiasie, in ag neem. Die satelliet se versteurde bewegingsvergelykings
is numeries ge-ïntegreer deur gebruik te maak van die sewe-agste orde Runge-Kutta-
Fehlberg metode wat fout-voortplanting inhibeer deur gebruik te maak van 'n aanpasbare
integrasiestaplengte. Die MSIS-90 atmosferies model, wat voorsiening maak vir dag-nag
en half-jaarlikse atmosferiese variasies, is gebruik vir die berekening van atmosferiese
digtheid. Sorg is gedra by die presiesie modellering van die beweging van die J2000
ekwator en ekwinokse. Resultate vir hierdie toetsgeval toon meer voortreflik te wees as
die SPG4 - en 'n kommersieël-beskikbare vooruitskatter.
Die langtermyn effekte van aard-afplatting en atmosferiese sleur op wentelbaanleeftyd is
ondersoek en toegepas op die wentelbaanverval-afskattingsprobleem. Wentelbaanverval
is bereken deur die integrasie van die tydsafgeleides van die wentelbaanelement onder
invloed van aard-afplatting en atmosferiese sleur. Vir die doel is 'n semi-analitiese
tegniek, wat gebruik maak van Gauss-Legendre kwadratuur en Runge-Kutta numeriese
integrasie, gebruik gemaak. Nodige rekenaar programmatuur is ontwi kkeI om die
vervalteorie te implimenteer. Optimale sleur-koëffisiënte is afgeskat deur van presiesie
wentelbaananalise gebruik te maak. Twee gevallestudies van bekende vervalde satelliete
is gebruik om die vervalteorie te evalueer. Resultate vir beide gevallestudies toon aan dat
eksperimentele resultate werklike vervaltye binne aanvaarbare limiete navolg.
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The quadrifilar helix antenna and its application to wide angle phase-steered arraysMarais, Sarel Jacobus 03 1900 (has links)
Thesis (MScIng)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The quadrifilar helix antenna has frequently been employed to provide the wide
angle, circularly polarized radiation pattern which is preferable for mobile satellite
communications. A detailed study of this antenna and its varieties is presented.
When used as an element in wide angle scanning arrays for aeronautical satellite
tracking applications, the additional requirement of a low profile with light weight
applies. This further complicates the realization of good circular polarization
close to the horizon.
A top disk is incorporated into various antenna structures in an effort to
improve the radiation performance when used within a closely spaced array while
reducing the height of the radiating element. The array performance of these
elements are investigated which hints at a supported traveling mode aiding the
ability to accomplish the wide angle beam steering. Subsequent study of leakywave
antennas initiated the study and implementation of leaky-wave structures
in phased arrays of quadrifilar helix elements. / AFRIKAANSE OPSOMMING: Die vierledige heliksantenna word dikwels gebruik vir toepassings wat ’n wye,
sirkulêr gepolariseerde stralingspatroon benodig. ’n Verskeidenheid van hierdie
antennas is noukeurig bestudeer en hul toepaslikheid vir mobiele sattelietkommunikasie
ondersoek. Wanneer hierdie antennas in fase gestuurde skikkings gebruik
word, word dit ook vereis dat die eenhede liggewig is met ’n lae profiel. Dit bemoeilik
die verkryging van goeie sirkulêre polarisasie naby die horison aansienlik.
In ’n poging om die wyehoek straling met kort antennas te verbeter, is ’n
oorhoofse skyf tot verskillende heliksstrukture toegevoeg. In nou gespasieerde
skikkings maak hierdie skywe ’n positiewe bydrae to wyehoekstralingeienskappe.
Die invloed van lekmodusse wat binne die struktuur voortplant is ondersoek en
gebruik in skikkings waarvan die bundel naby aan die horison gestuur word.
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