[USRP-users] Frequency resolution of UBX-160 with integer N mode

Andreas Leuenberger andreas.leuenberger at palindrome-rs.ch
Thu Mar 7 04:14:53 EST 2019


Hi Fabian

Thank you for your answer.
I have check the schematics of the X310. The reference clocks to the
daughter boards and the 200 MHz sampling clocks are both generated
by the "clock jitter clean" chip (LMK0481). I did not have time yet to
check the configuration of this chip, but probably you are right and
the reference clock to the daughter boards is not 10 MHz (as I assumed).
It could be 200 MHz or directly 50 MHz.

Best regards,
andreas


> Hi,
>
> please double check on that, as I am not 100% sure.
> As far as I was able to figure out, the LO is generated from the 
> Daughterboard internal 200 MHz reference (which is dirived from the 10 
> MHz), but is divided by 4 for some reason, so you get multiples of 50 
> MHz. This will also induce a random 90° phase shift between the signals, 
> which is a big problem for MIMO stuff.
> At least the TwinRX boards we used were able to share the LO between 
> multiple channels, which fixed the problem for us.
>
> Best regards,
> Fabian
>
> Am 04.03.2019 um 17:23 schrieb Andreas Leuenberger via USRP-users:
> >/Hello all, /> >//> >/I am using a USRP X310 with two daughter boards UBX-160 v2. To get a /> >/stable phase difference of the two daughter boards, I use the RX LOs in /> >/integer N mode ("mode_n=integer"). - I have noticed that the frequency /> >/step of the LO is 50 MHz. As the frequency of the reference signal is 10 /> >/MHz, I would expect a step of 10 MHz. /> >//> >/Is there a way to reduce this frequency step? /> >//> >/Thanks for your help, /> >/andreas /> >//> >//> >/_______________________________________________ /> >/USRP-users mailing list /> >/USRP-users at lists.ettus.com 
<http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com> />>/http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com /

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