On 06/13/2021 04:02 PM, Skyvalakis Konstantinos wrote:
Agreed. The compensation part is not the one I worry about. What
worries me the most is the angle-in-radians part.
Let's say that from the time sink plot I observe that I have pi/2
radians phase offset between channel 1 and channel 2. How do I know
it's pi/2 radians and not -3pi/2?
To be precise, I am also dumping the 2 channels complex data to 2 file
sinks, which I then import on matlab for easier and faster
experimentation.
In other words, how can I precisely calculate the 4 discrete phase
shifts I am observing in my application?
Should I use cross correlation?
Should I use Hilbert transform?
I don't have a very noisy application, in case that plays a very
crucial role.
Thanks.
If you consult the "uhd_fft" app within the gnuradio/gr-uhd source tree,
you'll see that it has a mode where it will display the
relative phases of two channels when you have a two-channel input.
It also has a bunch of different synchronization options,
so you can glean a lot of technique info from that.
Also, there's a fair amount of "stuff" out there on phase measurements
with Gnu Radio--this is just the first one that popped up
in a Google search:
https://www.egr.msu.edu/classes/ece480/capstone/spring14/group02/docs/Application%20Note%20-%20Phase%20George%20Godby%20Team%202.pdf
On Jun 13, 2021 22:06, Marcus D Leech <patchvonbr...@gmail.com> wrote:
Phase *correction* is easy once you know what that correction
should be. Just a complex multiply-const by
Complex(math.cos(angle-in-radians),math.sin(angle-in-radians))
Or the equivalent in complex exponential notation.
Sent from my iPhone
On Jun 13, 2021, at 1:52 PM, Skyvalakis Konstantinos
<kskyvala...@isc.tuc.gr> wrote:
Understandable. However, if you eventually hear anything about
it please let me know.
Can I contact you again tomorrow for some questions I have
about the phase correction block I need to make? (I mean
through discuss-gnuradio)
Thank you very much.
On Jun 13, 2021 19:37, Marcus D Leech
<patchvonbr...@gmail.com> wrote:
I haven’t heard fro R&D on it. Part of the problem is the N200
was designed over a decade ago, and the original engineering
team have long since departed…
Sent from my iPhone
On Jun 13, 2021, at 6:25 AM, Skyvalakis Konstantinos
<kskyvala...@isc.tuc.gr> wrote:
Hi Marcus and sorry for bothering you again, but I'd like
to ask if you have any news regarding my problem.
Thank you.
On Jun 11, 2021 16:15, Skyvalakis Konstantinos
<kskyvala...@isc.tuc.gr> wrote:
Yes it kind of helps, because if I manage to apply a
phase shifting/correction technique, then all 4 scenarios
could produce sensible data.
I am trying to build a phase correction block now, that
will compare the 2 received signals, to see which phase
shift out of the possible 4, minimizes the absolute phase
difference between the 2 channels.
After I figure out which phase offset is the correct one,
out of all 4, then I can run the rest of my
DoA application. It is a bit of a pain in the a**, but it
will have to do in case it never gets fixed.
Let me know if you have any news from Ettus.
Thanks again.
------------------------------------------------------------------------
*From:* Marcus D Leech <patchvonbr...@gmail.com>
*Sent:* Friday, June 11, 2021 4:05 PM
*To:* Skyvalakis Konstantinos
*Subject:* Re: Phase Synchronize 2 USRP N200 w/ SBX cards
Also does knowing that there are only 4 possible phase
relationships help in your application at all? Like only
one of the 4 possible phase assumptions can produce
“sensible” data? Just a thought.
Sent from my iPhone
On Jun 11, 2021, at 9:03 AM, Marcus D Leech
<patchvonbr...@gmail.com> wrote:
I am an Ettus support contractor. I have a direct
channel to R&D so I will relay any insights I receive
here since any such feedback would be generally useful.
Sent from my iPhone
On Jun 11, 2021, at 8:15 AM, Skyvalakis
Konstantinos <kskyvala...@isc.tuc.gr> wrote:
I also tried contacting Ettus Support but they
are not replying to my e-mails.
I will try to implement the phase calibration for now.
Thank you for your effort.
------------------------------------------------------------------------
*From:* Marcus D Leech <patchvonbr...@gmail.com>
*Sent:* Friday, June 11, 2021 2:23 PM
*To:* Skyvalakis Konstantinos
*Cc:* Discuss-gnuradio@gnu.org
*Subject:* Re: Phase Synchronize 2 USRP N200 w/
SBX cards
I have a query in to Ettus R&D about possible causes.
But you might need, for now to do an initial phase
Calibration when you start up.
Sent from my iPhone
On Jun 11, 2021, at 3:39 AM, Skyvalakis
Konstantinos <kskyvala...@isc.tuc.gr> wrote:
I repeated the experiments once again today
and I got once again the same results. I still
keep on randomly getting these 4 cases I
attached on a previous message.
I observed that cases 1.png and 3.png have a
phase difference of +/- 180 degrees
and cases 2.png and 4.png also have a phase
difference of +/- 180 degrees.
Do you reckon you could help me any further
with my problem? I really need to achieve this
synchronization for my thesis.
Thank you very much.
------------------------------------------------------------------------
*From:* Discuss-gnuradio
<discuss-gnuradio-bounces+kskyvalakis=isc.tuc...@gnu.org>
on behalf of Skyvalakis Konstantinos
<kskyvala...@isc.tuc.gr>
*Sent:* Friday, June 11, 2021 12:39 AM
*To:* Marcus D. Leech
*Cc:* Discuss-gnuradio@gnu.org
*Subject:* Re: Phase Synchronize 2 USRP N200
w/ SBX cards
Exactly my thoughts as well, I mean regarding
the phase ambiguity of the WBX daughterboards,
from what I've read on the Ettus website.
I am 100% sure the daughterboards are SBX.
On Jun 11, 2021 00:26, "Marcus D. Leech"
<patchvonbr...@gmail.com> wrote:
On 06/10/2021 01:00 PM, Skyvalakis
Konstantinos wrote:
In addition to my last message
regarding the INTEGER_N tuning, I
repeated the experiment multiple
times. I even restarted the USRPs and
the signal generator multiple times.
What I observed was, that there were
only 4 different recurring phase
offsets (Blue = RX2 of SBX1, Red = RX2
of SBX2).
I am attaching the 4 screenshots I
captured.
Thank you so much for your help. I
feel like we're getting there.
------------------------------------------------------------------------
You're sure that you have SBX cards and
not WBX cards? Sorry for the
apparently-stupid question, but the WBX
uses almost the
same hardware as the SBX, but uses a
2XLO mixer that has fixed phase
ambiguity--which would look like what you
have here.
