Ferran,
> The synchronization goal is in the order of ps level.
I'm glad you mentioned your requirements. Note that time synchronization at a
"ps level" is 3 to 4 orders of magnitude beyond what the typical commercial or
eBay or DIY GPSDO will do.
But as you imply, you're only using GPS to get close (ns levels) and then using
your own two-way communication to narrow it down to ps levels, right?
> Within the Report Packet 0x8F-AC, the bytes 16-19 indicate “Estimate of
> UTC/GPS offset”, is this the time difference ?
Yes. Section "A.10.31 Report Packet 0x8F-AC Secondary Timing Packet" says:
"PPS Offset: This field carries the offset of the PPS output relative to UTC
or GPS as
reported by the GPS receiver in nanoseconds. Positive values indicate that
the
ThunderBolt’s PPS is coming out late relative to GPS or UTC."
The range and precision of that time interval value would look something like
this:
http://leapsecond.com/pages/tbolt-8d/
I can send you the raw data if you want to play with it. Attached is a
histogram. Note the standard deviation is about 2 ns.
> My idea is to develop the control loop which will be able to synchronize one
> oscillator to another.
Remember that all the ingredients in your system will then need to be stable to
ps levels: the oscillator, the DAC, the 1PPS pulse, the cables, the input
signal conditioning, and time or phase comparator, etc. That's a pretty tall
order but not impossible.
You may want to synchronize using 10 MHz instead of 1PPS to reduce your noise
and improve the tight lock. How far apart are your two oscillators?
In case it helps your effort, see
https://en.wikipedia.org/wiki/The_White_Rabbit_Project and read the PDF's. It's
an open h/w project.
/tvb
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