Digital signal processing methods for large-N, low-frequency radio telescopes
<p>Current attempts to make precision measurements of the HI power spectrum at high redshifts have led to the construction of several low-frequency, large-<em>N</em>, interferometric arrays. The computational demands of digital correlators required by these arrays present a signifi...
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| Format: | Thesis |
| Language: | English |
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2014
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| _version_ | 1826281138567512064 |
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| author | Hickish, J |
| author2 | Jones, M |
| author_facet | Jones, M Hickish, J |
| author_sort | Hickish, J |
| collection | OXFORD |
| description | <p>Current attempts to make precision measurements of the HI power spectrum at high redshifts have led to the construction of several low-frequency, large-<em>N</em>, interferometric arrays. The computational demands of digital correlators required by these arrays present a significant challenge. These demands stem from the treatment of radio telescopes as collections of two-element interferometers, which results in the need to multiply <em>O</em>(<em>N</em><sup>2</sup>) pairs of antenna signals in an N-element array. Given the unparalleled flexibility offered by modern digital processing systems, it is apt to consider whether a different way of treating the signals from antennas in an array might be fruitful in current and future radio telescopes. Such methods potentially avoid the unfavourable <em>N</em><sup>2</sup> scaling of computation rate with array size.</p> <p>In this thesis I examine the prospect of using direct-imaging methods to map the sky without first generating correlation matrices. These methods potentially provide great computational savings by creating images using efficient, FFT-based algorithms. This thesis details the design and deployment of such a system for the Basic Element of SKA Training II (BEST-2) array in Medicina, Italy. Here the 32-antenna BEST-2 array is used as a test bed for comparison of FX correlation and direct-imaging systems, and to provide a frontend for a real-time transient event detection pipeline.</p> <p>Even in the case of traditional <em>O</em>(<em>N</em><sup>2</sup>) correlation methods, signal processing algorithms can be significantly optimized to deliver large performance gains. In this thesis I present a new mechanism for optimizing the cross-correlation operation on Field Programmable Gate Array (FPGA) hardware. This implementation is shown to achieve a 75% reduction in multiplier usage, and has a variety of benefits over existing optimization strategies.</p> <p>Finally, this thesis turns its focus towards The Square Kilometre Array (SKA). When constructed, the SKA will be the world's largest radio telescope and will comprise a variety of arrays targeting different observing frequencies and science goals. The low-frequency component of the SKA (SKA-low) will feature ~250,000 individual antennas, sub-divided into a number of stations. This thesis explores the impact of the station size on the computational requirements of SKA-low, investigating the optimal array configuration and signal processing realizations.</p> |
| first_indexed | 2024-03-07T00:24:17Z |
| format | Thesis |
| id | oxford-uuid:7d983fb3-9411-4906-92cd-70e2c1040b54 |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T00:24:17Z |
| publishDate | 2014 |
| record_format | dspace |
| spelling | oxford-uuid:7d983fb3-9411-4906-92cd-70e2c1040b542022-03-26T21:04:43ZDigital signal processing methods for large-N, low-frequency radio telescopesThesishttp://purl.org/coar/resource_type/c_db06uuid:7d983fb3-9411-4906-92cd-70e2c1040b54AstrophysicsEnglishOxford University Research Archive - Valet2014Hickish, JJones, MZarb Adami, K<p>Current attempts to make precision measurements of the HI power spectrum at high redshifts have led to the construction of several low-frequency, large-<em>N</em>, interferometric arrays. The computational demands of digital correlators required by these arrays present a significant challenge. These demands stem from the treatment of radio telescopes as collections of two-element interferometers, which results in the need to multiply <em>O</em>(<em>N</em><sup>2</sup>) pairs of antenna signals in an N-element array. Given the unparalleled flexibility offered by modern digital processing systems, it is apt to consider whether a different way of treating the signals from antennas in an array might be fruitful in current and future radio telescopes. Such methods potentially avoid the unfavourable <em>N</em><sup>2</sup> scaling of computation rate with array size.</p> <p>In this thesis I examine the prospect of using direct-imaging methods to map the sky without first generating correlation matrices. These methods potentially provide great computational savings by creating images using efficient, FFT-based algorithms. This thesis details the design and deployment of such a system for the Basic Element of SKA Training II (BEST-2) array in Medicina, Italy. Here the 32-antenna BEST-2 array is used as a test bed for comparison of FX correlation and direct-imaging systems, and to provide a frontend for a real-time transient event detection pipeline.</p> <p>Even in the case of traditional <em>O</em>(<em>N</em><sup>2</sup>) correlation methods, signal processing algorithms can be significantly optimized to deliver large performance gains. In this thesis I present a new mechanism for optimizing the cross-correlation operation on Field Programmable Gate Array (FPGA) hardware. This implementation is shown to achieve a 75% reduction in multiplier usage, and has a variety of benefits over existing optimization strategies.</p> <p>Finally, this thesis turns its focus towards The Square Kilometre Array (SKA). When constructed, the SKA will be the world's largest radio telescope and will comprise a variety of arrays targeting different observing frequencies and science goals. The low-frequency component of the SKA (SKA-low) will feature ~250,000 individual antennas, sub-divided into a number of stations. This thesis explores the impact of the station size on the computational requirements of SKA-low, investigating the optimal array configuration and signal processing realizations.</p> |
| spellingShingle | Astrophysics Hickish, J Digital signal processing methods for large-N, low-frequency radio telescopes |
| title | Digital signal processing methods for large-N, low-frequency radio telescopes |
| title_full | Digital signal processing methods for large-N, low-frequency radio telescopes |
| title_fullStr | Digital signal processing methods for large-N, low-frequency radio telescopes |
| title_full_unstemmed | Digital signal processing methods for large-N, low-frequency radio telescopes |
| title_short | Digital signal processing methods for large-N, low-frequency radio telescopes |
| title_sort | digital signal processing methods for large n low frequency radio telescopes |
| topic | Astrophysics |
| work_keys_str_mv | AT hickishj digitalsignalprocessingmethodsforlargenlowfrequencyradiotelescopes |