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QUESTION: Homebrew Spread spectrum
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March 31st 04, 05:32 AM
Laura Halliday
Posts: n/a
(Timothy C Holtom) wrote in message . com...
Can anyone out there tell me a good source of practical information
(schematics and the like) for building SS transmitters and receivers.
I'm particularly interested in how I'd design the part of the receiver
that acquires then tracks the synchronisation signal from the
transmitter (correlation etc)
How to synchronize to direct-sequence spread spectrum
should be obvious (think Costas Loop).
A sliding-window correlator is a common approach, other-
wise. 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.
Look in back issues of Wireless World from 1993 for a
fully worked-out example.
Laura Halliday VE7LDH "Que les nuages soient notre
Grid: CN89mg pied a terre..."
ICBM: 49 16.05 N 122 56.92 W - Hospital/Shafte
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