Subarrays

The continuum subarray option offers two 1 GHz baseband pairs with the 8-bit samplers in up to 3 subarrays or four 2 GHz baseband pairs with the 3-bit samplers, with the same spectral channel and polarization product options as are available for wideband observing. The setup for each subarray is completely independent in terms of observing frequency, polarization products, and integration times.

When using three subarrays, there are some restrictions on the number of antennas in each subarray. The Baseline Board in the correlator treats each set of 4 antennas independently, using a separate column of correlator chips. With 7 such columns, the correlator can handle up to 7×4 = 28 antennas. The correlator configuration software requires that a given column not be split across subarrays. For instance, one cannot observe with 9 antennas in each of 3 subarrays, because 9 antennas requires three columns (two with 4 antennas each, and one with 1 antenna); three subarrays of 9 antennas each would require 3×3 = 9 columns, two more than are actually available. Splitting the array into 11, 8, and 8 antennas is allowed.

For more information on subarrays, please see the Subarrays section in the Guide to Observing with the VLA.

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