I did an experiment similar to this a year or so ago. I synced all the USRPs to the same 10MHz and PPS. I had pretty good results using libgps to get the GPS time and then using UHD to start streaming on a particular PPS edge on all units. With LFRX boards this will ensure that the DDCs start at the same time and start from zero degrees. I seem to remember there was some small random variation from run to run. If you are just looking for relative changes in phase difference I found this approach works fairly well.
On Tue, Jun 17, 2014 at 10:36 AM, Martin Braun <martin.br...@ettus.com> wrote: > On 17.06.2014 19:06, David Miller wrote: > >> Hello, >> I want to measure the phase difference between three synchronised USRP >> channels (Common Ref & PPS), does software exist to do this, and to what >> accuracy, please? >> Sorry, this is a bit of a newbie question, and probably already covered! >> > > Sure, the easiest way would simply be to put in a scope, and check by > looking -- of course, that's not very accurate. > > There's enough math operators in GNU Radio to see the actual phase > difference, such as conjugate and multiply, then convert to phase. > > Cheers, > Martin > > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >
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