[alma-config] Pseudo random arrays

[Steven]

Dave Woody mentioned a cos squared distribution of antennas when discussing
pseudorandom arrays today. I did some analagous work in the optical domain
as part of my PhD which aimed to remove spectral orders from the power
spectra of pixellated spatial filters- clearly there is an analogy with
reducing sidelobes in the dirty beam of a radio interferometer, and indeed I
drew this analogy in ALMA memo 353 (available on line at
http://www.heddle97.freeserve.co.uk/rando/random.html). I mention this
mainly as at the time I submitted it, I got no notice from the memo
exploder, so there is fair chance nobody else did either. The memo presents
results from an extreme member of the ensemble of possible cos squared
distributions as a candidate for a compact array (and then tries to explain
why it isn't great!) My work on this kind of problem is covered in the first
two references of this memo, with the first reference in this memo showing
examples of power spectra from three different pseudo random distributions
including cos squared, a general analysis of randomised distributions and
also happily comes up with the result arrived at independently by Leonia and
Dave that maximum sidelobe level is inversely proportional to number of
antennas or pixels.

Hope this is helpful.

Cheers,
       Steven

Steven Heddle, Newington, Holm Road, Kirkwall, Orkney KW15 1PY
Tel: 01856 877119             Email: steven at kw15.co.uk
Fax: 0870 4039359           URL: http://www.kw15.co.uk