In the past few years, a possible new population of sources emitting fast and bright transient radio bursts have been discovered. To explore this new transient phase space, the next generation of radio telescopes, typically interferometers, provide wide observing bandwidths in order to achieve high sensitivity for the detection of weak sources and multi-beaming capabilities to increase the field of view. In comparison to a traditional single beam radio dish, these telescopes collect vast volumes of data and still rely on the traditional observing techniques. Localising transient events during their discovery is essential as these events might not be repeatable by nature. I describe the development and construction of a prototype phased array, the Manchester University Student Telescope (MUST), capable of multi-beam operation. I present results of the Yagi antenna beam measurements and the optimum antenna separations; the investigation of the radio frequency interference spectrum around the preferred observing band and setting the subsequent bandpass filter specifications; simulations of the optimum configurations of the MUST tiles; and finally I describe implementation of the digital back-end. For the joint task of discovery and simultaneous localisation, the advantages of single dishes and interferometers are combined in a beam forming approach. I present an investigation into the wide-bandwidth time-domain signal processing techniques for time-domain beamforming that can be used in transient and pulsar observations. I discuss the efficient polyphase decomposition for interpolation digital filters and multiplication-free fractional delay filters that can be used to reduce the complexity of the beamformer implementation and avoid high sampling rates. This reduced complexity allows more simultaneous beams to be formed using time-domain techniques. This analysis was performed for the MUST array, but is applicable to a wide range of interferometers. I have developed and analysed a new proof-of-concept non-imaging method to localise transient sources observed with interferometers or phased array feeds. It utilises the additional spectral and comparative spatial information obtained from multiple overlapping tied array beams. This allows us to estimatea transient source location with up to arc second accuracy in almost real time and allows the required high time resolution to be preserved. We demonstrate that this method can work for a variety of interferometric configurations, including for LOFAR and MeerKAT, and that the estimated angular position may be sufficient to identify a host galaxy, or other related object, without reference to other simultaneous or follow-up observations.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:647424 |
| Date | January 2015 |
| Creators | Obrocka, Monika |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | https://www.research.manchester.ac.uk/portal/en/theses/hightime-resolution-astrophysics-using-digital-beamforming(5293d2b8-2054-4d67-9fca-435f7482be31).html |
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