[asac] [almanews] ALMA Memo 383 Released

[Stacy Oliver]

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/alma335/memo335.pdf
Download a ps version of ALMA Memo 383.
	http://www.alma.nrao.edu/memos/html-memos/alma335/memo335.ps

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