Abstract
We report on the feasibility study of a W-band multibeam heterodyne receiver for the Sardinia Radio Telescope (SRT), a general purpose fully steerable 64-m diameter antenna located on the Sardinia island, Italy, managed by INAF (“Istituto Nazionale di Astrofisica,” Italy). The W-band front-end is designed for the telescope Gregorian focal plane and will detect both continuum and molecular spectral lines from astronomical sources and radio emission from the Sun in the 3 mm atmospheric window. The goal specification of the receiver is a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> focal plane array operating in dual-linear polarization with a front-end consisting of feed-horns placed in cascade with waveguide Orthomode Transducers (OMTs) and LNAs (Low Noise Amplifiers) cryogenically cooled at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx $ </tex-math></inline-formula> 20 K. The instantaneous FoV (Field of View) of the telescope is limited by the shaping of the 64-m primary and 7.9-m secondary mirrors. The cryogenic modules are designed to fit in the usable area of the focal plane and provide high-quality beam patterns with high antenna efficiency across the 70 – 116 GHz Radio Frequency (RF) band. The FoV covered by the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> array is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.15\times 2.15$ </tex-math></inline-formula> arcmin <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , unfilled, with separation between contiguous elements of 43 arcsec. Dual-sideband separation (2SB) down-conversion mixers are designed to be placed at the cryostat output and arranged in four four-pixel down-conversion modules with 4 – 12 GHz Intermediate Frequency (IF) bands (both Upper Side Band and Lower Side Band selectable for any pixel and polarization). The receiver utilizes a mechanical derotator to track the parallactic angle.
Highlights
TO THE SRTThe Sardinia Radio Telescope (SRT, www.srt.inaf.it) is a general-purpose fully steerable 64-m diameter radio telescope designed to operate with high efficiency across the 0.3-116 GHz frequency range [1]-[4]
The W-band receiver will utilize the Monitor and Control (M&C) unit and the build-to-print mechanical derotator developed by INAF
We reported on an advanced feasibility study of a W-band cryogenic multibeam receiver for the Gregorian focus of the 64-m diameter Sardinia Radio Telescope
Summary
The Sardinia Radio Telescope (SRT, www.srt.inaf.it) is a general-purpose fully steerable 64-m diameter radio telescope designed to operate with high efficiency across the 0.3-116 GHz frequency range [1]-[4]. Once equipped with such a receiver, the SRT will be one of the few large single-dish radio telescopes in the world capable of carrying out high-sensitivity spectral line and continuum mapping across the 3 mm atmospheric window. One of the initial INAF goals for the upgrade of the current set of SRT front-ends aimed at constructing a prototype W-band single-pixel receiver [15][17] to test the telescope active surface [18] and the metrology system to demonstrate observation capabilities up to the antenna highest design frequency (≈100 GHz). Separation configuration and beam spacing between projected beams in the range 2-5.7 × HPBW at all frequencies
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