[asac] [almanews] Correction to Memo 383 Release

[Carolyn White]

ALMA Memo #383

A Simple Technique for Disciplining Independent Demultiplexers

Marc Torres and Olivier Gentaz
IRAM (Grenoble) , France

2001-07-26

In every antenna of the ALMA array, the digitizers will deliver 3-bit (or
more) samples at the rate of 4 Gigasamples per second. Data is not
practical to handle at this speed and needs to be converted to a lower
frequency by means of serial-to-parallel conversion. To solve this problem
the telecomm industry has developed fast "mux/demux" chips, which
unfortunately are single-bit devices. If we use 3 (or more) of them, a
synchronisation problem arises. The right way of solving this problem
would be to design a chip including 3 (or more) demultiplexers on the same
die. Should this approach be found not economical for ALMA, this paper
describes a method for synchronizing several single-bit commercial
demultiplexers.  A prototype circuit including two single-bit devices has
been built and successfully tested. The measured timings for acquisition
and recovery are presented.

View a pdf version of ALMA Memo 383.
    http://www.alma.nrao.edu/memos/html-memos/alma383/memo383.pdf

Download a ps version of ALMA Memo 383.
    http://www.alma.nrao.edu/memos/html-memos/alma383/memo383.ps



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