hi jonathan,
as you pointed out, for a phased array feed, where the correlator is
used only to calibrate the beamformer coefficients,
you don't need to compute all the possible cross correlations,
and you don't have to do the computation it in real time.
the calibration time scale requirement depends on wavelength, and
atmospheric and instrument fluctuations.
for the ATA i think billy barrot implemented a
1 by 8 correlator that could switch around to correlate
any 8 antennas against a master antenna (a 1 by 8 correlator).
it took a while to get all the calibration cross correlation
measurments done this way, but it worked well.
i think now, billy has implemented a slightly
larger correlator to speed the calibration up.
best wishes,
dan
On 1/8/2011 2:28 PM, Jonathan Landon wrote:
Has anyone created a correlator that only correlates overlapping
subsets of the antenna inputs? Suppose I have 32 inputs and want to
correlate 1-16, 8-24, 16-32. For a large phased array feed it may
only be necessary to correlate relatively near neighbors. The benefit
of correlating subsets comes if it's easier to build three 16-input
correlators than one 32-input correlator. If it's true that only
subsets are needed for a large phased array feed, then complexity and
resource usage grows linearly as the number of inputs is increased,
instead of exponentially. The drawback of course is that such an
architecture could be so complicated that it just translates
computational burden into longer development time and complexity.
Does anyone have a sense if this may be a bad idea or if anyone has
done it?
Thanks,
Jonathan Landon
