MILLIMETER WAVE
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Last Modified: Monday, 12-December-05 1:05:31 PM EDT




This material is based on work supported by the National Science Foundation under Grant AST-0096854.

Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect those of the National Science Foundation.


System Description

  • Unique, ultra-wideband receiver designed to search for highly redshifted spectral lines from very distant galaxies
  • Covers 74-110.5 GHz bandwidth with a receiver/spectrometer system yielding 31 MHz resolution
  • Two dual polarization feeds with full band ortho-mode transitions (effectively four separate receivers)
  • High speed Faraday rotation beam switch to minimize 1/f noise
  • Back-end spectrometer is an analog autocorrelator with 6.5 GHz bandwidth per section and 6 sections per receiver, which provides 146 GHz total bandwidth!

Redshift Search Strategy

  • The early universe is indicated by highly redshifted galaxies.
  • These galaxies are easy to identify using bolometers, but bolometers provide no redshift (Z) information.
  • The strongest spectral lines are from CO (N x 115 GHz) and C (492 GHz, 810 GHz). This receiver will search the entire band simultaneously for these and other lines of interest.
  • High Z galactic spectral lines are expected to be quite weak, therefore there is no reason to search at frequencies of high absorption.
  • The 74-110.5 GHz bandwidth lends a high probability of detecting one line from galaxies with Z > 1.1, and two lines from galaxies with Z > 3.


System noise temp with Trcvr= 60 K and 2 and 5 mm PWV.




Block diagram of the front end.
Blue components are at 20K, red at room temperature outside the dewar.


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