On 2021-08-19 10:11 p.m., [email protected] wrote:
Thanks, Marcus. This is what support told me as well. What is the
purpose of the EXT REF on the B205-mini if not for synchronization? Is
it only to have a higher frequency accuracy for standalone application?
Pretty-much, yes. There were hopes that it could be used for
cross-device synchronization, but the DPLL in the FPGA simply isn't up
to the task. The
residual mutual phase-noise is just too much.
I intend to phase-calibrate an antenna on the ground by flying the
B205-mini around it on a drone. I intend to use GPSDOs on the drone
and on the ground for frequency synchronization. I imagine if the mini
won’t work I’ll have to use another B210 instead (which is another
engineering headache to deal with).
Phase calibration shouldn't require a calibrator that is synchronous to
the receivers--the receivers need to be synchronous to each other. I've
done
something similar (without the drone) using an external noise
generator based on a B2xx. But even something like a diode noise
generator and
directional coupler right up at the antenna should work.
Turn on the noise generator, use fast convolution to compute the
cross-correlation, and derive the delays and phases.
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