Theses and dissertations (Engineering and Built Environment)
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Item Development of a two element correlating radio telescope interferometer(2015) Callaghan, David James; MacPherson, Stuart David; Sokoya, O.A two element correlating radio telescope interferometer is the fundamental building block of modern radio telescope aperture synthesis arrays. Early radio telescopes consisted of a single antenna, usually a dish antenna. Larger and larger antennas were constructed in order to improve the resolution of the measurement of the direction and extent of radio frequency radiation coming from the sky. Telescope resolution is fundamentally limited by the ratio of the telescope aperture to the wavelength of the received radiation. For single element radio telescopes to approach the resolution of their optical telescope counterparts, they would need to be impractically large. Mathematical analysis of correlating two element radio telescope interferometers shows that very large aperture radio telescopes can be synthesized from a number of two element interferometers. An array of two element correlating radio telescope interferometers can be used to produce a synthesized aperture equal to the largest distance between two receiving antennas in the array. Telescope arrays thus enable very high resolution since the angular resolution of a telescope is proportional to the wavelength of the received signal divided by the aperture diameter. A spread of separation distances between antenna pairs is required to produce a complete image of the radiating sources in the field of view. Modern digital signal processing techniques can be used to provide cost effective performance and flexibility in two element correlating radio telescope interferometer design. The aim of this research project was to design and construct a two element correlating radio telescope interferometer using modern digital signal processing techniques and hardware. The relevant theory has been investigated together with suitable hardware and software platforms and tools used to produce such a system. The two element correlating radio telescope interferometer produced, will be used as a platform for further investigative research into its design, performance and application. The outcome of this research project was the successful completion of a working two element correlating radio telescope interferometer. The development process has been analysed and carefully documented. Some fringe measurements for a simple single frequency radiating point source have been taken and these measurements have been analysed according to theoretical expectation. Potential for further research, using the two element correlating radio telescope interferometer produced, has been identified and discussed.Item Development of a multi-frequency interferometer telescope for radio astronomy (MITRA)(2015) Ingala, Dominique Guelord Kumamputu; MacPherson, Stuart David; Sokoya, O.This dissertation describes the development and construction of the Multi-frequency Interferometer Telescope for Radio Astronomy (MITRA) at the Durban University of Technology. The MITRA station consists of 2 antenna arrays separated by a baseline distance of 8 m. Each array consists of 8 Log-Periodic Dipole Antennas (LPDAs) operating from 200 MHz to 800 MHz. The design and construction of the LPDA antenna and receiver system is described. The receiver topology provides an equivalent noise temperature of 113.1 K and 55.1 dB of gain. The Intermediate Frequency (IF) stage was designed to produce a fixed IF frequency of 800 MHz. The digital Back-End and correlator were implemented using a low cost Software Defined Radio (SDR) platform and Gnu-Radio software. Gnu-Octave was used for data analysis to generate the relevant received signal parameters including total power, real, and imaginary, magnitude and phase components. Measured results show that interference fringes were successfully detected within the bandwidth of the receiver using a Radio Frequency (RF) generator as a simulated source. This research was presented at the IEEE Africon 2013 / URSI Session Mauritius, and published in the proceedings.