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- Title
Low-Cost, Low-Loss, Ultra-Wideband Compact Feed for Interferometric Radio Telescopes.
- Authors
MacKay, Vincent; Lai, Mark; Shmerko, Peter; Wulf, Dallas; Belostotski, Leonid; Vanderlinde, Keith
- Abstract
We have developed, manufactured, and tested a new feed design for interferometric radio telescopes with "large-N, small-D" designs. Such arrays require low-cost and low-complexity feeds for mass production on reasonable timescales and budgets, and also require those feeds to be compact to minimize obstruction of the dishes, along with having ultra-wide frequency bands of operation for most current and future science goals. The feed presented in this paper modifies the exponentially tapered slot antenna (Vivaldi) and quad-ridged flared horn antenna designs by having an oversized backshort, a novel method of maintaining a small size that is well-suited for deeper dishes (f ∕ D ≤ 0. 2 5). It is made of laser cut aluminum and printed circuit boards, such that it is inexpensive (≲ 7 5 USD per feed in large-scale production) and quick to build; it has a 5:1 frequency ratio, and its size is approximately a third of its longest operating wavelength. We present the science and engineering constraints that went into design decisions, the development and optimization process, and the simulated performance. A version of this feed design was optimized and fabricated for the Canadian Hydrogen Observatory and Radio-transient Detector (CHORD) prototypes. When simulated on CHORD's very deep dishes (f ∕ D = 0. 2 1) and with CHORD's custom first-stage amplifiers, the on-sky system temperature T sys of the complete receiving system from dish to digitizer remains below 30 K over most of the 0.3–1.5 GHz band, and maintains an aperture efficiency η A between 0.4 and 0.6. The entire receiving chain operates at ambient temperature. The feed is designed to slightly under-illuminate the CHORD dishes, in order to minimize coupling between array elements and spillover.
- Subjects
BROADBAND communication systems; INTERFEROMETRY; RADIO telescopes; RADIO astronomy; INDUSTRIAL efficiency
- Publication
Journal of Astronomical Instrumentation, 2023, Vol 12, Issue 4, p1
- ISSN
2251-1717
- Publication type
Article
- DOI
10.1142/S2251171723500083