Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Beamforming is a technique used to combine signals from an array of antennas to effectively
synthesize a single aperture and beam. In the Radio Astronomy community the
technique is used to obtain a desirable beam pattern as well as to electronically point the
beam of an array. Next generation radio telescopes such as the Square Kilometre Array
(SKA) surpass current technology and will extensively make use of beamforming techniques.
Various factors determine the output of a beamformer; however, given an array with a
fixed configuration only the weights applied to the incoming signals affect the synthesized
aperture and beam. Furthermore, the incoming data must be processed in real-time, at a
rate equal to the input-output rate of the processor. Both the weighting function and the
real-time implementation of beamforming, are the primary subjects of this thesis.
In this thesis various deterministic weighting functions are investigated. The algorithms
are implemented in a matlab program, serving as a simulation tool for investigating the
techniques. The program is verified by comparing the expected theoretical outcomes to
the simulated output. For the program the following functionalities are included: a steering
technique, spectral weighting, Dolph-Chebychev, and the Least Square Error algorithm. Applications
of these techniques is investigated and their prominence in the Radio Astronomy
community is established.
For the real-time beamformer implementation, the UniBoard platform configured with
beamformer firmware, is investigated. This is important as the UniBoard is an excellent
example of a beamformer implementation within the Radio Astronomy community. The
architecture is used to emulate a linear array by implementing a python control script,
where the output corresponded accurately with the expected theoretical values.
The thesis also constitutes the design and implementation of a digital frequency domain
beamformer on the ROACH board. This processing board is employed by the Karoo Array
Telescope (KAT-7) in South Africa. This work is therefore important as it demonstrates a
beamformer implementation on an architecture in use by the Radio Astronomy community.
An antenna array is designed and built for the verification of the beamformer design. Results
with a good degree of accuracy were obtained and where errors exist they are discussed. / AFRIKKANSE OPSOMMING: Bundelvorming is ’n tegniek waarmee die seine van ’n antenna samestelling gekombineer
word om ’n enkele effektiewe stralingsvlak en stralingspatroon te sintiseer. In die Radio Astronomie
gemeenskap word die tegniek gebruik om ’n gewenste stralingspatroon te sintiseer
sowel as om die rigting van die patroon elektronies te beheer. Die Square Kilometre Array
(SKA) is ’n toekomstige radioteleskoop en sal grootliks gebruik maak van bundelvorming
tegnieke.
Die uitset van bundelvormers word geaffekteer deur verskeie faktore, maar vir ’n gegewe
samestelling is dit net die gewigsfunksies wat toegepas word op die inkomende seine wat
die gesintiseerde patroon kan beheer. Verder moet die inkomende data verwerk word teen
’n tempo gelykstaande aan die inset-en-uitsetkoers van die verwerker. Die gewigsfunksie so
wel as die implementasie van die bundelvormer is albei primêre onderwerpe van die tesis.
’n Verskeindenheid van deterministiese bundelvormingstegnieke sal ondersoek word in
hierdie tesis. Die algoritmes is in ’n matlab program geïmplementeer vir simulasie doeleindes.
Die program is geverifieër deur die uitset te vergelyk met die verwagte teoretiese
waardes. Die program sluit die volgende funksies in: ’n rigting beheer algoritme, spektraalgewigte,
Dolph-Chebychev, en die minste vierkantsfout algoritme. Hierdie tegnieke is van
belang weens hul toepassing in die Radio Astronomie gemeenskap.
Vir die implementasie van ’n bundelvormer is die UniBoard hardeware, geprogrameer in
’n bundelvormings modus, van gebruik gemaak. Hierdie aspek is belangrik omdat die Uni-
Board ’n goeie voorbeeld van ’n geïmplementeerde bundelvormer in die Radio Astronomie
gemeenskap is. Die UniBoard word gebruik om ’n lineêre samestelling te emuleer deur in
python ’n beheer skrip te skryf, waar die uitset van die emuleerder akkuraat ooreenstem
met die verwagte waardes.
Die tesis behels ook die ontwerp en implementasie van ’n digitale frekwensiegebied bundelvormer
op die ROACH platform. Hierdie verwerker word tans gebruik in die Karoo Array
Telescope (KAT-7) in Suid-Afrika. Hierdie werk is dus belangrik omdat dit die implementasie
van ’n bundelvormer op tegnologie wat huidiglik in die Radio Astronomie gemeenskap
gebruik word demonstreer. Daarbenewens is ’n antenna samestelling ontwerp en gebou om
die bundelvormer te verifieër. Die resultate is akkuraat tot ’n redelike mate. Waar daar ’n
fout onstaan het word dit in die tesis bespreek.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96126 |
| Date | 12 1900 |
| Creators | Van Tonder, Vereese |
| Contributors | Davidson, David B., Stellenbosch University. Faculty of Engineering. Department of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | xvii, 115 p. : ill. |
| Rights | Stellenbosch University |
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