On 02/11/2019 06:34 PM, Aravind Dhulipalla via USRP-users wrote:
Hi Marcus,
Yes, I am following the link and using an external 10MHz and 1pps
reference signals. The way I am trying to synchronize is to have two
usrp's transmit different sine waves one with constant phase and the
other with a varying phase from 0 to 360degrees. I am calculating the
sum of amplitudes of the received signals and the phase at which the
amplitude sum is maximum will be the phase offset. By following this
approach I am getting a phase offset between 0 to 3 degrees. But when
I issue the next stream command with sine wave of calculated phase
offset I am seeing a huge phase difference between them anywhere
between 0 to 180 degrees for each run. I am not sure if my approach is
a correct one.
Thanks
Aravind.
I cannot quite parse what you're doing.
Are you saying the *mutual phase* offset changes between runs, or that
the phase measured *between runs* changes?
I would totally expect some phase-offset unpredictability between two
B210s. They aren't designed to have a predictable phase in that sense,
because
of the way the synthesizers work. They have no phase-resynch, and
since a fractional-N PLL synthesizer "naturally" doesn't lock at any
particular phase-angle relative to the reference, no two PLL
synthesizers, even if seeing EXACTLY THE SAME REFERENCE FREQUENCY, can
be guaranteed to have a predictable-and-low phase-offset after tuning,
even if tuned at "exactly" the same time.
On Sun, Feb 10, 2019 at 12:59 AM Marcus Müller
<[email protected] <mailto:[email protected]>> wrote:
Hi Aravind,
first of all, have you seen
http://files.ettus.com/manual/page_sync.html ?
You'll find in the last paragraph that after each tuning, your phase
relationship between different B210s will be random, but constant for
the run (aside from minor PLL drift).
So, you need to tune, and then calibrate; how that can be done depends
on the system you're building.
Best regards,
Marcus
On Fri, 2019-02-08 at 17:03 -0800, Aravind Dhulipalla via USRP-users
wrote:
> Hi,
>
> Has anyone achieved phase synchronizing between two usrp b210's
using
> external reference and pps? If yes I would appreciate any help
that I
> can get.
>
> Thanks
> Aravind.
>
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