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Heterodyne instrumentation upgrade at the Caltech Submillimeter Observatory

Kooi, J. W. and Kovács, A. and Bumble, B. and Chattopadhyay, G. and Edgar, M. L. and Kaye, S. and LeDuc, R. and Zmuidzinas, J. and Phillips, T. G. (2004) Heterodyne instrumentation upgrade at the Caltech Submillimeter Observatory. In: Millimeter and Submillimeter Detectors for Astronomy II. Proceedings of SPIE. No.5498. Society of Photo-optical Instrumentation Engineers (SPIE) , Bellingham, WA, pp. 332-348. ISBN 9780819454300.

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Balanced receivers are under development at the Caltech Submillimeter Observatory (CSO) for the 230/460 GHz and 345/660 GHz atmospheric windows. The mixers are tunerless, implemented in a balanced configuration, have a 4-8 GHz IF, and can be used in dual frequency observation mode. As shall be seen, the balanced arrangement provides a high level of amplitude noise immunity and allows all of the available LO power to be used. In turn, this permits complete automation of the receivers by means of synthesized LO source(s). A disadvantage of balanced mixers is, perhaps, that the sidebands at the IF remain convolved (DSB), unlike sideband separating (2SB) receivers. The latter, however are unbalanced and do not have the noise and LO injection advantages of balanced mixers. For the CSO, balanced mixers covering the range 180-720 GHz were judged most promising to facilitate many of the astrophysical science goals in the years to come. In parallel, a dual polarization 280-420~GHz continuous comparison (correlation) receiver is in an advanced state of development. The instrument has two beams on the sky; a reference and a signal beam. Using only cooled reflecting optics, two polarizing grids, and a quadrature hybrid coupler, the sky beams are coupled to four tunerless SIS mixers (both polarizations). The 4-12 GHz mixer IF outputs are, after amplification, correlated against each other. In principle, this technique results in flat baselines with very low RMS noise, and is especially well suited for high redshift Galaxy work. Not only do these changes greatly enhance the spectroscopic capabilities of the CSO, they will also enable the observatory to be integrated into the Harvard-Smithsonian Submillimeter Array (SMA), as an additional telescope.

Item Type:Book Section
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Kooi, J. W.0000-0002-6610-0384
Chattopadhyay, G.0000-0001-7942-5025
Additional Information:© 2004 Society of Photo-Optical Instrumentation Engineers (SPIE). We wish to thank NiklasWadefalk for his help with the IF components, Martin Houde for his input on (thermally) stabilized IF amplification, and Richard Chamberlin for useful insights in the multitude of system related issues. This work was supported in part by NSF Grant# AST-0229008.
Funding AgencyGrant Number
Subject Keywords:Balanced mixer theory, continuous comparison receiver, radial probe, full-height waveguide to thin-film microstrip transition, split-block, high current density superconducting-insulating-superconducting (SIS) tunnel junction, broad bandwidth quadrature waveguide hybrid, DC-break, IF match, Wilkinson in phase power combiner, Low noise amplfier (LNA), 4-8 GHz intermediate frequency (IF)
Series Name:Proceedings of SPIE
Issue or Number:5498
Record Number:CaltechAUTHORS:20180801-133517472
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Official Citation:Jacob W. Kooi, Attila Kovacs, Bruce Bumble, Goutam Chattopadhyay, Michael L. Edgar, Steve Kaye, Rick LeDuc, Jonas Zmuidzinas, Thomas G. Phillips, "Heterodyne instrumentation upgrade at the Caltech Submillimeter Observatory", Proc. SPIE 5498, Millimeter and Submillimeter Detectors for Astronomy II, (8 October 2004); doi: 10.1117/12.552539;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:88467
Deposited By: George Porter
Deposited On:01 Aug 2018 21:40
Last Modified:16 Nov 2021 00:27

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