On 03/22/2019 05:31 AM, Janos Buttgereit via USRP-users wrote:
Hi,
after having struggled a lot with network config issues I finally got out N310
up and running. We chosed it for an application that needs perfectly constant
phases between all four channels to build up DOA estimation applications.
I’ve set up an N210 as a signal source, outputting a sine round about 1.5GHz
feeding a 4-way splitter that than feeds all four input channels of the N310. A
Rhode&Schwarz signal generator outputting a 3GHz sine wave feeds a two way
splitter that is connected to both external rx LO inputs.
From this setup I expect all four channels to maybe have a static phase offset
that does not change over time. However, it can be noticed that the pairs of
channels 0 and 1 and the pairs of channels 2 and 3 show those behavior but both
pairs drift against each other over time. Any idea of what could be wrong with
this setup?
I attached the GNURadio flow graph for this setup.
Thanks in Advance!
Change the "Sync" option to "Unknown PPS". Why this is required is a
bit of a mystery, but another user experienced the same issue.
The N310 is conceptually two radios in a single box, and each radio
within the FPGA has its own "timekeeper". For some reason, unless those
"timekeepers" are started synchronized with each other, sample
timestamps drift relative to one another. This should not be the case, but
it appears to be.
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