A Wideband Quad-Ridge Flared Horn Feed Design for the Square Kilometre Array Band 1
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Fundamental physics, MSc
Publicerad
2016
Författare
Flygare, Jonas
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The vast and unimaginable greatness of the universe will never stop to amaze us humans. A strive to know, explore or just to grasp the concept of space will always drive us, both philosophically and technically. As a result of this, the visions and advances in radio astronomy for the foreseeable future are very optimistic and a significant part of this will be realized in the Square Kilometre Array project (SKA). The objective is to create the world’s largest radio telescope array through interferometry with thousands of telescopes in the deserts of Australia and South Africa. A portion of these will be designated to single-pixel feeds on Gregorian offset reflector dishes. The band covering 350−1050 MHz is defined as SKA Band 1 and is within the region of the general Ultra High Frequency (UHF) band. This is a very challenging area in radio astronomy due to the great amounts of radio-frequency interference (RFI) from cellphones, television broadcast and global navigation satellite systems (GNSS) at these frequencies. To minimize interference we require radio silent environments, and to account for other environmental effects such as the atmosphere and cosmic radiation, we need high-level optimized systems. This combination enables us to detect weak outer space sources with a radio telescope. We show the development of a wideband Quad-Ridge Flared Horn (QRFH) feed for Band 1 and how it fulfills our specified requirements. We discuss the properties of the QRFH and focus on the trade-off in reducing spill-over together with a high aperture efficiency on an offset dual reflector. For the lower end of the frequency band in focus, there is a strong contribution of noise from the sky, which increases the challenges in the system design. The main objective, which is high sensitivity, is achieved with an average Aeff/Tsys > 4.2 m2/K across the 3 : 1 frequency band and an input reflection better than −10 dB. Development of the feed is largely based on stochastic optimization with parametrized QRFH feed models. The customizable spline horn profile and the power of genetic algorithms is explained with an emphasis on particle swarm optimization (PSO).We also briefly mention the transfer of the electromagnetic design of the feed, into a mechanical prototype which was finished early in 2016. In late June the same year it was shipped to Penticton, Canada and the Dominion Radio Astrophysical Observatory (DRAO) where it was mounted on the DVA-1, an early prototype reflector for the SKA. At 11.30 AM Pacific Standard Time (PST) on the 22nd of June 2016, we received first light with a sweep over the radio source Cassiopeia A.
Beskrivning
Ämne/nyckelord
Astronomi , Grundläggande vetenskaper , Elektroteknik , Elektrofysik , Astronomy , Basic Sciences , Electrical engineering , Electrophysics