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Optimization of a reverberation chamber performance through different simulated stirrer designs
Bothma, A. 2025. Optimization of a Reverberation Chamber Performance Through Different Simulated Stirrer Designs. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/24ab1567-2fd4-43ac-b6ec-ba2d6d25b720
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| Format: | Thesis |
| Language: | English |
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Stellenbosch : Stellenbosch University
2025
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| _version_ | 1867613786731446272 |
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| access_status_str | Open Access |
| author | Bothma, Aneshka |
| author2 | Gilmore, Jacki |
| author_browse | Bothma, Aneshka Gilmore, Jacki |
| author_facet | Gilmore, Jacki Bothma, Aneshka |
| author_sort | Bothma, Aneshka |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Bothma, A. 2025. Optimization of a Reverberation Chamber Performance Through Different Simulated Stirrer Designs. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/24ab1567-2fd4-43ac-b6ec-ba2d6d25b720 |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/132116 |
| institution | Stellenbosch University (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:41:41.074Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2025 |
| publishDateRange | 2025 |
| publishDateSort | 2025 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/132116 Optimization of a reverberation chamber performance through different simulated stirrer designs Bothma, Aneshka Gilmore, Jacki Wiid, P. G. Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. Electromagnetic compatibility Electromagnetic reverberation chambers Mixing machinery UCTD Bothma, A. 2025. Optimization of a Reverberation Chamber Performance Through Different Simulated Stirrer Designs. Unpublished masters thesis. Stellenbosch: Stellenbosch University [online]. Available: https://scholar.sun.ac.za/items/24ab1567-2fd4-43ac-b6ec-ba2d6d25b720 Thesis (MEng)--Stellenbosh University, 2025. ENGLISH ABSTRACT: Given the sensitivity levels at which astronomy science is conducted, the government declared the Square Kilometer Array site in South Africa a Radio-Frequency Quiet Zone. Thus, Radio Frequency Interference from intentional and unintentional transmitters on or near the site severely threatens radio astronomy science. One way the South Africa Radio Astronomy Observatory’s RFI team mitigates the potential RFI risks on site is by doing meticulous RFI qualification measurements on all electronic devices/systems deployed to the site. These RFI qualification measurements a redone inside an electromagnetic compatibility chamber called a Reverberation chamber. However, the SARAO RFI team has identified a potential limitation related to the horizontal stirrer in their chamber, raising measurement accuracy concerns. The chamber was designed to operate at the lowest usable frequency of 181 MHz. However, the measurement accuracy in a reverberation has recently been desired down to 50 MHz. Therefore, designing a possible stirrer to solve the problem and optimise the chamber performance in the lower frequency range was imperative. Given that there is no transparent methodology for stirrer designs, the complex theoretical modal description of the reverberation chamber was studied to understand its full performance potential. A few global stirrer techniques were also researched to determine a base stirrer design implemented in FEKO simulation software. Simulation models of a reverberation chamber incorporating a stirrer design made it possible to alter it and assess the resultant chamber performance. This repeated process enabled identifying an optimal stirrer design for one of SARAO’s chambers. The stirrer design modifications included changes to its orientation, the configuration of joined or separated plates, the implementation of plates at various angular references, increased stirrer diameter, and the addition of flanges to a smaller stirrer to achieve comparable chamber performance. The findings concluded that a vertical stirrer results in just as practical chamber performance as a horizontal stirrer. The arrangement of stirrers featuring discrete plate separation led to undesired chamber performance at the frequency corresponding to a wavelength that matches the distance between the plates, indicating that the signals at that frequency do not reflect in a different direction with each stirrer step. If a stirrer with separated plates is used as the design, the chamber performance results will only be good when the plates are randomized with different angular adjacent. One crucial finding was that stirrers with an enlarged diameter improve the chamber performance, especially the LUF, which is essential and related to the problem statement of the project. Adding flanges to a smaller diameter stirrer impacts the chamber’s performance and LUF just as significantly, indicating a possible implementation strategy without replacing a complete stirrer design. A stirrer design was recommended for the SARAO RFI team’s newest reverberation chamber. The three SARAO reverberation chambers with three different stirrers were calibrated, and their performance was evaluated and compared. Even though the simulation results show the enlarged diameter of the stirrer is the best solution, the practical comparison and validation measurements showed that the stirrer-to-chamber volume ratio should be considered. The verification and validation of the performance of the newest SARAO chamber show minimal measurement error margin in the low-frequency band and achieve the desired LUF. AFRIKAANSE OPSOMMING: Gegewe die sensitiviteit waarby sterrekunde wetenskap gedoen word, het die regereing die gebied waar die Square Kilometer Array radio-teleskoop geleë is as ‘n radiofrekwensie-stil zone verklaar. Dus, het radiofrekwensie-inmenging van opsetlike en onbedoelde instrumente op of naby die terrein ‘n ernstige bedreiging op radio sterrekunde wetenskap. Een manier waarop die Suid-Afrika Radio Sterrekunde-sterrewag se RFI span aanspreek maak op potensiële RFIrisiko’s op die terein, is deur noukeurige RFI kwalifikasie m eetings t e doen op alle elektroniese toestelle of stelsels wat na die terin gestuur word. RFI kwalifikasie meetings word b inne ‘ n e lektromagnetiese b ekwaamheids kamer gedoen, met die naam weerkaats-kamer. Die SARAO RFI span het ’n potensiële beperking geïdentifiseer wat verband hou met die horisontale r oerder in hul kamer, wat kommer wek oor metingsakkuraatheid. Die kamer is ontwerp om teen die laagste bruikbare frekwensie van 181 MHz te werk. Onlangs is die vereiste op meting akkuraatheid in ’n weerkaatskamer verlaag tot 50 MHz. Daarom was dit noodsaaklik om ’n moontlike roerder te ontwerp om die problem op te los sowel as om die kamer se gedrag in die laer frekwensie reeks te optimeer. Aangesien daar geen deursigtige ontwerp metode van ‘n reorder is nie, is die komplekse teoretiese modale beskrywing van die weerkaatskamer bestudeer om die volle potensiaal van die kamer te verstaan. Daar was ook ‘navorsing gedoen op n paar wêreldwye roerings tegnieke, om ‘n basiese roerontwerp te bepaal wat gebruik was in FEKO simulasie sagteware. Deurmiddel van simulasiemodelle van weerkaats kamers met ‘n reorder ontwerp te gebruik, was dit moontlik om die roerderontwerp te verander en die kamer se gedrag te evalueer. Hierdie herhalende proses het dit moontlik gemaak om ‘n optimale roerontwerp vir ‘n SARAO kamer te identifiseer. Die roerderontwerp veranderinge sluit die oriëntasie van die roerder in, die konfigurasie van die plate vas of los van mekaar, die implementeering van plate by verskillende hoek verwysings, vergrootte deursnee en die byvoeging van addisionele klein plate om ‘n vergelykbare kamergedrag te behaal. Die bevindinge het tot die gevolgtrekking gekom dat ’n vertikale roerder net so effektiewe kamer gedrag lewer as ‘n horisontale reorder. Die rangskikking van roerders met diskrete plaatskeiding, het gelei tot ongewenste kamerprestasie by die frekwensie wat ooreenstem met ’n golflengte gelyk aan die afstand tussen die plate, wat aandui dat die seine by daardie frekwensie nie gereflekteer word in verkillende rigtings met elke roer stap nie. As ‘n roerder met geskeide plate wel gebruik word, sal die kamer gedrag resultate net goed wees wanneer die plate teen verkillende hoeke grens relatief tot mekaar. Een deurslaggewende bevinding was dat roerders met ’n vergrote deursnee die kamerprestasie verbeter, veral die LUF, wat noodsaaklik is en verband hou met die probleemstelling van die projek. Die byvoeging van eksta stukkies plaat by ‘n roerder met ‘n klein deursnee, het ‘n soortgelyke impak op die kamer se prestasie en LUF gehad. Dit stel dus ‘n implementeringstegniek voor sonder om ‘n hele roerder te vervang. ‘n Roerder ontwerp was aanbeveel vir die SARAO RFI span se nuutste weerkaatskamer. Die drie SARAO weerkaatskamers met drie verskillende roerders is gekalibreer, en hul werk verrigting is geëvalueer en vergelyk. Selfs al toon die simulasie resultate dat die vergrote deursnee van die roerder die beste oplossing is, het die praktiese vergelyking en bevestiging meetings getoon dat die roerder-tot-kamer volume verhouding in ag geneem moet word. Die verifikasie en bevestiging van die gedrag van die nuutste SARAO kamer toon minimale meetfoute in die lae-frekwensie gedien en bereik die verwagte LUF. Masters 2025-05-26T06:17:47Z 2025-05-26T06:17:47Z 2025-03 Thesis https://scholar.sun.ac.za/handle/10019.1/132116 en Stellenbosch University xv, 119 pages : illustrations application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Electromagnetic compatibility Electromagnetic reverberation chambers Mixing machinery UCTD Bothma, Aneshka Optimization of a reverberation chamber performance through different simulated stirrer designs |
| title | Optimization of a reverberation chamber performance through different simulated stirrer designs |
| title_full | Optimization of a reverberation chamber performance through different simulated stirrer designs |
| title_fullStr | Optimization of a reverberation chamber performance through different simulated stirrer designs |
| title_full_unstemmed | Optimization of a reverberation chamber performance through different simulated stirrer designs |
| title_short | Optimization of a reverberation chamber performance through different simulated stirrer designs |
| title_sort | optimization of a reverberation chamber performance through different simulated stirrer designs |
| topic | Electromagnetic compatibility Electromagnetic reverberation chambers Mixing machinery UCTD |
| url | https://scholar.sun.ac.za/handle/10019.1/132116 |
| work_keys_str_mv | AT bothmaaneshka optimizationofareverberationchamberperformancethroughdifferentsimulatedstirrerdesigns |