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27 November 2002 Operational performance of the EVLA LO round-trip phase system
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The goal of the Expanded Very Large Array (EVLA), project is to upgrade a world-class astronomical instrument in the meter-to-millimeter wavelength bands. The project combines modern technologies with the sound design of the existing Very Large Array (VLA) to increase by an order of magnitude the sensitivity, resolution, and frequency coverage of the existing instrument. This paper discusses the techniques used to maintain phase coherence of the EVLA system. The enhancements to the VLA system include improved feeds and receivers, new Local Oscillator (LO) and Intermediate Frequency (IF) systems, a fiber optic LO distribution system, high speed digitizers, 10Gbps digital links, a dense wavelength division multiplexed fiber transmission system, and a new high speed correlator. The phase requirement for the LO system requires that a phase stability of 2.8 picoseconds per hour at 40 GHz be maintained across the entire array. To accomplish this, a near real time continuous measurement will be made of the phase delay in the fiber optic cable distributing the LO reference signals to each antenna. This information will be used by the correlator to set the delay on each of the baselines in the array.
© (2002) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Steven J. Durand and Terry Cotter "Operational performance of the EVLA LO round-trip phase system", Proc. SPIE 4845, Advanced Global Communications Technologies for Astronomy II, (27 November 2002);


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