[Discuss-gnuradio] Phase Synchronization Across Channels in X310

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

 

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