Beamforming is central to the processing function of all phased arrays and becomes particularly challenging with a large number of antenna element (e.g. >100,000). The ability to beamform efficiently with reasonable power requirements is discussed in this paper. Whilst the most appropriate beamforming technology will change over time due to semiconductor and processing developments, we present a hierarchical structure which is technology agnostic and describe both Radio-Frequency (RF) and digital hierarchical beamforming approaches. We present implementations of both RF and digital beamforming systems on two antenna array demonstrators, namely the Electronic Multi Beam Radio Astronomy ConcEpt (EMBRACE) and the dualpolarisation all-digital array (2-PAD). This paper will compare and contrast both digital and analogue implementations without considering the deep system design of these arrays.
The surveying speed of large reflectors can be increased by one or two orders of magnitude when the focal fields are sampled with a dense phased array. In a dense array consisting of a large number of antenna elements (100 up to 1000), multiple beams can be synthesised and steered electronically. This collecting and manipulating of the entire electric field in the focal plane creates the possibility of a simultaneously improvement in the efficiency of existing telescopes and open up wide fields-of-view. This paper will describe the first results of the EU project FARADAY. The approach chosen in FARADAY is to use a Vivaldi array of 72 antenna elements configured in 8x9 grid. The analogue beamformer, integrated with the antenna array, syntheses beams by using for example 3x3 elements combined in three rings, where each ring is given a specific weight factor. The number of beams has been limited to two in this demonstrator project. Further more we will explore the possibilities and limitations of the large-scale use of Focal Plane Arrayís, in particular for the fourteen 25-meter reflectors of the Westerbork Syntheses Radio Telescope (WSRT).Keywords: Radio Astronomy, dense focal plane array, focal field sampling, conjugate field matching, aperture efficiency of a prime-focus reflector.
Abstract-Developments in radio astronomy instrumentation drive the need for lower cost front-ends due to the large number of antennas and low noise amplifiers needed. This paper describes cost reduction techniques for the realization of antennas and low noise amplifiers in combination with a noise budget calculation for array systems in the absence of cryogenic cooling.
Aperture Arrays (AA) mark a new era in radio astronomy combining high sensitivity with a large field-ofview, enabling very high survey and imaging speeds. This paper describes the development of low frequency aperture arrays leading up to SKA phase 1 within the Aperture Array Verification Program (AAVP) as part of the SKA program.
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