----- Original Message -----
From: "Laura Halliday"
Newsgroups: rec.radio.amateur.homebrew
Sent: Tuesday, March 30, 2004 8:32 PM
Subject: QUESTION: Homebrew Spread spectrum


How to synchronize to direct-sequence spread
spectrum should be obvious (think Costas Loop).

A sliding-window correlator is a common approach,
otherwise. Three correlators in parallel. One runs
a little ahead, one is on time, the third runs a
little behind.

The LO free-runs (deliberately) a little slow or
fast. When the locally-generated PN sequence lines
up with the received sequence, the outputs from the
early/late correlators track the LO, while the
on-time correlator provides the output.



Thanks for the info, Laura. I never did any work with a Direct sequence
system, but this makes a lot of sense.


Jim Pennell
N6BIU