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The Square Kilometre Array - Aperture Array Mid-frequency instrument will be surveying the southern hemisphere skies with unprecedented sensitivity in the mid 2020s at frequencies from 400MHz up to the 21 cm Hydrogen line. The University of Cambridge is developing a sparse random array solution based on log-periodic dipole array antennas within the Aperture Array Design Consortium. This type of array...
We report characterization results for an engineering prototype of a next-generation low-frequency radio astronomy array. This prototype, which we refer to as the Aperture Array Verification System 0.5 (AAVS0.5), is a sparse pseudorandom array of 16 log-periodic antennas designed for 70–450 MHz. It is colocated with the Murchison widefield array (MWA) at the Murchison radioastronomy observatory (MRO)...
In this paper we present the recent advances on the design of sparse arrays using log-periodic antennas for the SKA AA-Mid instrument. The SKA AA-Mid instrument will explore the southern hemisphere sky from ∼400 MHz up to 1.4 GHz with unprecedented sensitivity and survey speed. Large collecting area, low system noise and great survey speed are key to achieve the demanding requirements of the SKA....
We present an in-situ antenna characterization method and results for a “low-frequency” radio astronomy engineering prototype array, characterized over the 75–300 MHz frequency range. The presence of multiple cosmic radio sources, particularly the dominant Galactic noise, makes in-situ characterization at these frequencies challenging; however, it will be shown that high quality measurement is possible...
This paper describes the advantages and disadvantages of differential feeding of an antenna for low-frequency radio astronomy in the context of the SKA-low telescope. A series of practical measurements to test the correct functionality of the antenna + differential amplifier pair are described and results are presented and discussed.
Modern aperture array radio-telescopes at MHz frequencies (like the SKA-low instrument) will be made of a very large number of wideband antennas possibly arranged in an irregular configuration, with many imperfections to be corrected for, like mutual coupling. Here, low-order beam representations of array beams are given by using simulated embedded element radiation patterns, multiplied by low-order...
This paper provides an overview of the Aperture Array Verification System 0.5 (AAVS 0.5), co-located and operated in conjunction with the Murchison Widefield Array (MWA) near the Australian SKA core site. AAVS 0.5 is based on log-periodic antennas of a type potentially useful in next-generation low-frequency arrays such as SKA-low. We report on our progress by discussing results obtained thus far...
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