Sorry for comming late to the party...
This may be relevant:
http://phk.freebsd.dk/loran-c/CW/
The basic idea is that you use a high-rate ADC, something like 1MS/s
and then you average into for instance a 1msec = 1.000 samples circular
buffer.
That gives you a very narrow comb filter for all frequencies which
are a multiple of 1 kHz, and extracting the phase from, for instance
the 60 kHz WWVB carrier will be trivial.
In the example above, the buffer were w full second long, 1.000.000
samples, this reveals the per-second modulation of the carrier, and
allows you to extract any (averaged) signal on an integral Hz carrier
frequency.
There are Arm chips out there now with 1MSPS*12bit ADCs that's
plenty for this kind of stuff. (see also: http://phk.freebsd.dk/AducLoran/)
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
[email protected] | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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