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Proceedings Paper

The CARMA correlator
Author(s): David W. Hawkins; David P. Woody; B. Wiitala; J. Fredsti; K. P. Rauch
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Paper Abstract

The Combined Array for Research in Millimeter-wave Astronomy (CARMA) requires a flexible correlator to process the data from up to 23 telescopes and up to 8GHz of receiver bandwidth. The Caltech Owens Valley Broadband Reconfigurable Array (COBRA) correlator, developed for use at the Owens Valley millimeter-wave array and being used by the Sunyaev-Zeldovich Array (SZA), will be adapted for use by CARMA. The COBRA correlator system, a hybrid analog-digital design, consisting of downconverters, digitizers and correlators will be presented in this paper. The downconverters receive an input IF of 1-9GHz and produce a selectable output bandwidth of 62.5MHz, 125MHz, 250MHz, or 500MHz. The downconverter output is digitized at 1Gsample/s to 2-bits per sample. The digitized data is optionally digitally filtered to produce bands narrower than 62.5MHz (down to 2MHz). The digital correlator system is a lag- or XF-based system implemented using Field-Programmable Gate Arrays (FPGAs). The digital system implements delay lines, calculates the autocorrelations for each antenna, and the cross-correlations for each baseline. The number of lags, and hence spectral channels, produced by the system is a function of the input bandwidth; with the 500MHz band having the coarsest resolution, and the narrowest bandwidths having the finest resolution.

Paper Details

Date Published: 8 October 2004
PDF: 12 pages
Proc. SPIE 5498, Millimeter and Submillimeter Detectors for Astronomy II, (8 October 2004); doi: 10.1117/12.552430
Show Author Affiliations
David W. Hawkins, California Institute of Technology (United States)
David P. Woody, California Institute of Technology (United States)
B. Wiitala, California Institute of Technology (United States)
J. Fredsti, California Institute of Technology (United States)
K. P. Rauch, Univ. of Maryland/College Park (United States)


Published in SPIE Proceedings Vol. 5498:
Millimeter and Submillimeter Detectors for Astronomy II
Jonas Zmuidzinas; Wayne S. Holland; Stafford Withington, Editor(s)

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