BAORadio: A digital pipeline for radio interferometry and 21 cm mapping
  of large scale structures
  3D mapping of matter distribution in the universe through the 21 cm radio
emission of atomic hydrogen HI is a complementary approach to optical surveys
for the study of the Large Scale Structures, in particular for measuring the
BAO (Baryon Acoustic Oscillation) scale up to redshifts z < 3, and therefore
constraining dark energy parameters. We propose a novel method to map the HI
mass distribution in three dimensions in radio, without detecting or
identifying individual compact sources. This method would require an instrument
with a large instantaneous bandwidth (> 100 MHz) and high sensitivity, while a
rather modest angular resolution (~ 10 arcmin) should be sufficient. These
requirements can be met by a dense interferometric array or a phased array
(FPA) in the focal plane of a large primary reflector, representing a total
collecting area of a few thousand square meters with few hundred simultaneous
beams covering a 20 to 100 square degrees field of view. We describe the
development and qualification of an electronic and data processing system for
digital radio interferometry and beam forming suitable for such instruments
with several hundred receiver elements.
