The specifications for a new correlator are still under discussion
(see Chapter 5), as is the architecture best suited to meet them. It
is not yet clear whether the more appropriate architecture is a lag
correlator, as presently used at the VLA, or an FX correlator, as used
by the VLBA. A detailed design study is needed to choose between the
two options. Note that the product of the number of antennas, 
,
and the maximum bandwidth, 
, analyzed by the correlator is 
GHz. This ``figure of merit'' for the correlator is
comparable to that of the Millimeter Array (
= 80 GHz);
both correlators will be at least an order of magnitude larger than
the existing VLA correlator ( = 5.4 GHz) or the VLBA
correlator ( = 2.6 GHz).
The new correlator should be able to process data from at least 32 antennas and have enough delay to accommodate baselines up to 500 km. It could then process some combination of the twenty-seven VLA antennas, two or three of the innermost VLBA antennas (those at Pie Town, Los Alamos, and Fort Davis), and up to four new antennas on baselines between those in the VLA and in the VLBA (§1.2.5).