Expanding the field of view: station design for the AAMID SKA radio telescope
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Expanding the field of view: station design for the AAMID SKA radio telescope Jan Geralt Bij de Vaate 1,2 Wim A. van Cappellen 1
& Dirk
I. L. de Villiers 2 & David B. Davidson 2,3 &
Received: 10 October 2019 / Accepted: 12 October 2020/ # Springer Nature B.V. 2020
Abstract The new generation radio telescopes, such as the Square Kilometre Array (SKA) currently under construction, will use aperture array, technology for the low frequency regime. For SKA2, the second phase scheduled after the realization of SKA1, aperture array technology is proposed up to 1.4 GHz. The antenna element count, as well as the signal processing cost, of such a system will be high. In this paper we analyze an option to reduce the number of antenna elements by making the array sparse. To reduce the signal processing cost Fast Fourier Transform Beamforming is proposed and it performance is compared to traditional beamforming. To guide the system design a Figure of Merit for the performance cost ratio is proposed and evaluated for various levels of sparsity of the antenna array. It is concluded that, for equal front-end and back-end costs, a sparse system is only marginally better than a dense system. Only when signal processing cost is significantly lower than the front-end hardware, a sparse system can be competitive. Keywords Antenna arrays . Telescopes . Signal processing . Radio astronomy . FFT
beamforming . SKA
1 Introduction Aperture Arrays (AA) can be considered an enabling technology, or even a paradigm shift, in the development of next generation radio telescope systems [1]. They enable moving away from large reflectors, in which the signal is concentrated by means of the reflector, to a fully electronically steerable telescope. In AA’s each antenna element
* Jan Geralt Bij de Vaate [email protected]
1
The Netherlands Institute for Radio Astronomy (ASTRON), Dwingeloo, the Netherlands
2
Dept. Electrical and Electronic Engineering, Stellenbosch University, Stellenbosch, South Africa
3
ICRAR-Curtin University, Perth, Australia
Experimental Astronomy
observes a large fraction of the visible sky; electronic beamforming is used to concentrate signals to form one or more beams. AA’s are not new to radio astronomy - large arrays were built in the 1960s; however, fully electronically steerable systems are a recent development. Of these new generation AA radio telescopes the LOFAR telescope is the largest system currently in operation [2]. AA’s for radio astronomy have several advantages, including multi-beaming capability, operational flexibility, a large Field of View (FoV), and no moving parts. In the Square Kilometer Array (SKA) project, AA technology will be used to realize SKA1-Low which has a frequency range of 50 to 350 MHz [3]. SKA1-Low is part of the first phase of SKA. For the full SKA, SKA2, AA’s are proposed for higher frequencies as well, up to 1.45 GHz: the AA midfrequency telescope (AAMID). The multi beaming capability and the large FoV of an AA system comes at the cost of a large number of antennas, receivers, b
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