Browsing by Author "Bij de Vaate, Jan Geralt"

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    Expanding the field of view: station design for the AAMID SKA radio telescope
    (Stellenbosch : Stellenbosch University, 2019-12) Bij de Vaate, Jan Geralt; De Villiers, D. I. L.; Davidson, D. B.; Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering.
    ENGLISH ABSTRACT: The discovery of radio astronomy dates back to 1928, when Karl Jansky made the first detection of cosmic noise static. Radio astronomy is therefore a relatively young science and its development is completely in parallel with the radio technology enhancements, including the modern information technology. Radio astronomy has been often at the forefront; the first adopters of new technologies and capabilities. Very often radio astronomy triggered inventions that have been of direct use for other sciences and society. With the advent of digital signal processing, faster and smaller computers, radio astronomy has progressed at a very high pace. Arrays are being designed and built that contain thousands of individual antennas, connected and processed with digital signal processing, enabling very high performance. The conception of the Square Kilometre Array can be directly linked to the potential of Aperture Arrays (AA). As early as 1994 first sketches of the Square Kilometre Array consisted of flat electronically steerable panels. This AA telescope, briefly called the HI telescope, after the HI resonant line at 1421 MHz, would run from 150 to 1450 MHz. Although AAs are technically feasible, SKA1 will use dishes for the frequencies above 350MHz. This dissertation addresses the requirements, system design and possible implementation of an AA system for the SKA2, the second phase of the square kilometre array project. Aperture Arrays have the potential of instantaneous all-sky observations, creating a very powerful telescope. However, the realization of this telescope is not without challenges in cost, power consumption and operational performance. The research in this dissertation explores the potential of the sparse-regular array concept. Sparse-regular arrays are in use for lower frequency telescopes but implementation of this concept has not been considered for higher frequencies; up to the HI line at 1421 MHz. It will be argued with a new proposed figure of merit, average sensitivity divided by system cost, that a sparse-regular design can be superior to a dense or sparse-random system. This dissertation therefore provides an alternative solution for aperture arrays for the SKA and in particular focusses on a possible realization. A realization which takes signal processing into account that goes a step further than ‘just’ build a telescope that can do the same as dishes, but a bit better. For this it is proposed to use Fast Fourier Transform signal processing, enabled by a regular antenna placement structure. FFT signal processing will reduce the processing load significantly and fully utilizes the potential of AA’s. Therefore, regular arrays, sparse or dense, will be lower in cost and power consumption and superior in performance when compared to random arrays. This dissertation concludes that the sparse-regular concept, although technically feasible, has a number of significant drawbacks and therefore might not be the design of choice for SKA2.