Characterization of RF signal coupling into MeerKAT telescopes

[摘要] ENGLISH ABSTRACT: The study of weaker astronomical waves originating from billions of light years awaycould give an insight into the dawn of the universe's history. This requires the useof highly sensitive radio receivers and large radio telescopes for the detection of suchmysterious signals. The MeerKAT facility will form part of the square kilometre array(SKA) which will have orders of magnitude greater sensitivity than existing radio telescopes.However, radio frequency interference (RFI) becomes a concomitant worry to such sensitiveequipment.The proximity of adjacent structures of the MeerKAT dishes at the core area, provides apossibility of a high inter-coupling problem between the nearby dishes, even from low-levelemissions due to currents on structure cables. This thesis focuses on the electromagnetic(EM) characterization of a single dish using a physical scale model and computationalelectromagnetic (CEM) modelling. Together witheld measurements, the veri ed CEMmodel can be used for further investigations into coupling between MeerKAT antennas.The South African SKA has ensured that care is taken in the shielding design of criticalareas on the MeerKAT structure including the receiver indexer (RI) and cable entrypoint (stub-up). Due to the extreme sensitivity of the project, we qualify the shieldinge ectiveness with computational and scale modelling and on{site radio frequency (RF)coupling investigations on the MeerKAT dish structures.The CEM code FEKO and method of moments frequency domain numerical techniqueis utilised throughout the study. The FEKO model veri cation is successfully achievedthrough measurement of a physical scale model in an anechoic chamber. The validatedCEM model is con dently used to complementeld measurements. A good correlation isattained between measurement and simulation through the transfer function determinedfrom an incident electriceld and the associated coupled currents on di erent cables thatroute to the RI and the earth cable at the stub{up region.The veri ed CEM model can now be used for dish to dish coupling studies which willpredict the nature of EM environment at the core site and lead to possible recommendationsbefore the full commissioning of the entire array of MeerKAT antennas.

[发布机构] Stellenbosch University