On 08/19/2018 08:11 PM, Zhan Yanjun wrote:
Hello Marcus,
Thanks for the reply. Yes, I do expect that there will be a constant
phase offset that I will be able to compensate offline, however, the
issue here is that everytime I start a new recording, the phase
difference across the cards (and even between the 2 channels in the
card) is *always* different. I would expect it to be the same
everytime I record a signal.
Regards,
YJ
So, I would recommend looking at this app-note here, since gr-doa
requires that all channels be phase-synchronous with zero phase-offset:
https://kb.ettus.com/Direction_Finding_with_the_USRP%E2%84%A2_X-Series_and_TwinRX%E2%84%A2
The gr-doa demonstrator code is here:
https://github.com/EttusResearch/gr-doa
*From:*Discuss-gnuradio
<discuss-gnuradio-bounces+zyanjun=dso.org...@gnu.org> *On Behalf Of
*Marcus D. Leech
*Sent:* Saturday, 18 August 2018 02:32
*To:* discuss-gnuradio@gnu.org
*Subject:* Re: [Discuss-gnuradio] Phase Synchronization Across
Channels in X310
On 08/17/2018 05:37 AM, Zhan Yanjun wrote:
Hello everyone,
A while ago I came across an issue in running GNURadio with my
version of UHD and I have followed instructions from the Ettus
website
https://kb.ettus.com/Building_and_Installing_the_USRP_Open-Source_Toolchain_(UHD_and_GNU_Radio)_on_Linux
<https://kb.ettus.com/Building_and_Installing_the_USRP_Open-Source_Toolchain_%28UHD_and_GNU_Radio%29_on_Linux>
Now the UHD version is UHD_3.11.0.HEAD-0-ga1b5c4ae, and the
Gnuradio is version 3.7.13.4, and everything runs fine.
Everything was done on a fresh installation of Ubuntu 18.04.1 LTS.
Now, I want to do synchronous recording of all 4 channels on one
X310 SDR chassis, but when I check the phase of the signal at each
channel, they are not in phase.
Initially, I thought that it should have something to do with the
internal LO, so I tried various combinations of the LO configuration:
1.Internal, companion, companion, companion
2.Internal, companion, external, external
3.Internal, companion, external, companion
4.all internal
But, it still does not work. I have connected the LO RF cables in
a criss-cross fashion inside the chassis as well to pass the LO
configuration to the neighbouring 2 channels.
Attached here is a snapshot of the GNURadio flowchart I designed
for that purpose.
I also tried to install the latest UHD version in my computer, but
it is unable to work with FPGA image (non-release version).
Because the X310 are not mine, I cannot update FPGA image.
Have you all come across this issue before? Please share your
views on this, any help is much appreciated! I have tried
installing and reinstalling the programs a few times, but the
conclusion is still the same, and the phases across the channels
do not match.
Thanks and regards,
YJ
Don't forget that the LO link cables are of non-zero length
electrically, so there will be some phase offset between the two cards
that you'll need
to compensate for.
_______________________________________________
Discuss-gnuradio mailing list
Discuss-gnuradio@gnu.org
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
