On 10/06/2020 10:29 PM, Zeng, Huacheng via USRP-users wrote:
Hello:
I am using N310 for 4x4 MIMO transmission. Are N310's 4 TX/RX channels
internally synchronized for MIMO applications? Does it need an
external device (e.g., OctoClock-G CDA-2990) to synchronize those 4
channels for MIMO applications?
I am also exploring channel reciprocity using N310. I have successful
experience with SBX in the implementation of channel calibration. But
it seems WBX does not fit for this purpose because of some phase
ambiguity issue (if I remember correctly). Would the daughterboards in
N310 have the phase ambiguity issue?
Many thanks in advance!
Hua
The N310 has a pair of AD9371 RFFE chips. Those chips have two channels
each, and those channels are coherent with respect to each other.
There will be an unknown phase offset due to the nature of
(particularly Frac-N) synthesizers between the channels of the two halves.
Unless the N310 channels implement phase-resynch via timed commands (I
don't think that they do), you'd need some external method for
phase-aligning those channels.
Now because they're using a common reference clock, once the phase
offset has been factored out they should be in perfect synchronization
both in time and phase from that point forward.
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