On 04/23/2015 06:06 PM, Pengyu Zhang wrote:
I followed the suggestions and plotted the received baseband signal in
the IQ constellation. The phase offset of the baseband received by the
two RX antennas are still not constant... Attached are the update flow
graph and python program. Would be great if you can take a look again.
Thanks.
On Thu, Apr 23, 2015 at 3:06 PM, <mle...@ripnet.com
<mailto:mle...@ripnet.com>> wrote:
If you have the Octoclock-G connected to both units, then you
don't need to use the MIMO cable.
Make sure that both mboards have "external" for both the reference
clock and pps selections, and that "device time" is set to
"unknown PPS" for both of them.
On 2015-04-23 14:49, Pengyu Zhang wrote:
Hi,
I am working on phase coherent reception using 2 USRP N210s where
each is mounted with a SBX. The 2 N210s are connected via a MIMO
cable. 10MHz reference clock and PPS are generated by an
OctoClock-G and are fed into each N210. In this experiment, a TX
antenna transmits a constant signal to 2 RX antennas. I want to
obtain coherent phases at the 2 RX antennas. Attached is the flow
graph I am executing. It seems that I cannot achieve coherent
phase at the 2 Rx antennas. Any suggestions? Thanks.
Pengyu
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If you want phase-coherency, the two USRP sources *must* be part of the
same multi_usrp object--you have them as separate sources. One
can think of a multi_usrp object as also providing a common
"coherency domain".
Also, even when you do that, the "timed commands" feature in UHD,
specifically designed to zero-out phase *offset* for the SBX and WBX and
UBX boards, isn't, as far as I recall, something that gr-uhd does
automatically, so it isn't available in a GR flow-graph. Martin Braun
can correct
me if I'm wrong.
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