On 11/01/2023 13:45, David Raeman wrote:
Hello,
I’m working on a project that involves phase-coherent reception across
multiple E320 radios. I’m currently operating with a common clock
(provided by an Octoclock) and cabled RF connections. I understand
there will be some unknown phase offset between radios which changes
across power cycles and re-tunes, but I’m expecting that relationship
to be otherwise stable (neglecting temperature and other environmental
effects). I’m trying to track down what I /think/ is a frequency
difference between receive radios which changes between across RX
captures, even though I do not disconnect or re-tune between (although
I do use the same port for TX between these receptions).
If you aren't using timed streaming across radios (and I'm not sure
whether this is possible with E320), you're going to
have random phase relationships every time you restart your streams,
even though you haven't power-cycled.
What about just within a single radio?
I disable the I/Q balance tracking for the receive channels. Beyond
that, I’m wondering whether the AD9361 has other active tracking loops
or anything that happens between RX/TX turnaround which would lead to
this behavior. This same experiment/codebase did not have this
discrepancy when run on N200/SBX radios some time ago, which is why I
suspect some mechanism in the RFIC.
On a related note, I’m also looking at how to peek/poke the AD9361
register interface on an MPM radio. As far as I can trace, the data
flow is something like:
* Application calls into the UHD API
* UHD sends an RPC requests to the radio
* A Python service on Zynq PS handles the RPC request and calls into
native libusrp-periphs.so library
* libusrp-periphs.so library includes exported symbols from the 9361
C++ driver
So in order to make any changes to the AD9361 driver on the E320, I’d
need to cross-compile the UHD C++ libraries on the radio. Is there an
easier path I’m overlooking, or barring that, any documentation on the
appropriate environment/toolchain/procedure to rebuild the libraries
on the radio?
Thanks,
--
David Raeman
Synoptic Engineering
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