[USRP-users] about phase alignment btw Tx and Rx

Michael West michael.west at ettus.com
Fri Dec 26 18:01:47 EST 2014


Hi Min,

It is difficult to say what may be happening without knowing a little bit
more information.  Are you doing a loopback from Tx to Rx (through antennas
or direct cable)?  What is your sample rate, frequency, etc...?  Can you
provide a code snippet of the UHD commands you are using in each execution?

Best regards,
Michael


On Thu, Dec 25, 2014 at 10:37 PM, 天杨 闵 <usrp-users at lists.ettus.com> wrote:
>
> Hello everyone:
>
> This is Min.
> I am using USRPN210 to make a channel sounder right now, the daughterboard
> which I am using
> is SBX.
>
> A synchronization of frequency and timing is successful at this moment.
> However, the problem that I am facing is phase alignment btw Tx and Rx.
> I already set the Tx and Rx to start at a specific time by using timed
> command (set_start_time (uhd.time_spec()).
> I think the cordics in each device should be aligned with respect to each
> other.
> but there still existed phase offset after each execution.
> if this phase offset doesn't change (stable), then I can tune the phase of
> received signal
> to align it with Tx.
> the problem is the phase offset is changing after each execution.
> I run execution for 15 times, the maximum phase offset is around 10
> degrees.
> what should I do to solve this problem?
> could you please give me some help
>
> thanks in advance
>
> Min
>
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> USRP-users at lists.ettus.com
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>
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