Doctoral Degrees (Electrical and Electronic Engineering)

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Browsing Doctoral Degrees (Electrical and Electronic Engineering) by browse.metadata.advisor "Davidson, David"

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    Characterising the electromagnetic environment of MeerKAT
    (Stellenbosch : Stellenbosch University, 2017-03) Phiri, Temwani Joshua; Davidson, David; Wiid, Gideon; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: MeerKAT is South Africa’s 64-dish precursor radio telescope to the Square Kilometre Array (SKA), currently under construction in the semi-desert Karoo region. As these are new generation instruments, their specifications far exceed those of existing telescopes and thereby increases their susceptibility to radio frequency interference (RFI). So far, much has been accomplished in terms of electromagnetic compatibility (EMC) interventions. However, surveys in the recent past have indicated the need to examine signal propagation in the Karoo in greater detail. In particular, reliable predictive tools are essential in order to fully characterize the environment which is changing gradually as infrastructure development progresses. As a matter of first importance, selected empirical propagation models were statistically assessed by comparison to measurements in the Karoo. Based on the root mean square error (RMSE) values, the transmission loss predictions were deemed reliable. In spite of this, the limitations of empirical modelling were apparent: failure to accurately model real ground, inability to incorporate scattering phenomena and inadequacy in representing underlying physical processes. To meet the accuracy demands of the South African SKA Project (SKA-SA) pertaining to characterising the complex environment of MeerKAT, a deterministic model exploiting full-wave and asymptotic techniques was developed. Referred to simply as a ray model, this solution utilised the method of moments (MoM) to determine antenna characteristics and solve for real ground, while physical optics was utilised to address scattering from the dishes. With the software FEKO as the interface and simulation engine, the MeerKAT core was reproduced computationally. Analysis of the numeric data revealed the full extent of electromagnetic complexity in relation to multipath. Most notably, high spatial resolution attenuation maps were generated, revealing high and low risk regions. This has benefits for identification of potential RFI problems. The ray model showed very good performance when examined against measurements (RMSE <4 dB). This is highly advantageous since numerical modelling allows a lot more flexibility than physical testing permits. In particular, the novelty and significance of this research is the ability to reproduce an actual deployment scenario with precision and high accuracy.