On 2/16/2016 6:44 PM, Jeff Liebermann wrote:

This one?
http://www.google.com/patents/US8774317
It appears to be specific to a receiver that does both AM and BPSK. It
would seem that a BPSK only receiver could be sold. I've written some
things about the problem in the distant past. I'll see if I can find
my rants. The basic problem is that Xtendwave promised to sell or
sub-license a suitable chip, but hasn't. Vaporwa
http://finance.yahoo.com/news/xtendwave-announces-first-shipment-sample-171151210.html
http://www.xtendwave.com (broken web site?)
https://www.febo.com/pipermail/time-nuts/2014-July/085445.html

I read it a bit more closely and I think demodulating the phase carrier
will not infringe this patent. The patent refers to demodulation of the
phase aligned to the PWM/ASK modulation scheme. The NIST spec says the
phase inverts 100 ms after the ASK bit starts and so is not "aligned" in
that way. If you simply demod the BPSK without regard to the ASK bits I
can't see how it would be infringing the patent.

My thought was always to sample the signal at a high rate and analyze
the data in 100 ms blocks or smaller. My main concern is to get a good
resolution of the transitions traded off against processing gain. LCDs
are happy with a 30 Hz backplane rate so that would be a convenient value.

I just realized that the actual second change will need to be offset
from the transition of the phase change by 100 ms... in the wrong
direction. "Hey, the second updated 100 ms ago!"

Durn Google patents lets you download a PDF, but you can't copy text,
just images of the text. Otherwise I would quote and comment on a bit
more.

--

Rick