[USRP-users] Ettus UBX-160 vs SBX-120

Marcus Müller marcus.mueller at ettus.com
Mon Jul 3 05:12:38 EDT 2017


Hi Kyeong Su Shin!

Exactly that's what's happening; the 160 MHz wide low pass filter is
insufficient to function for a (complex) ADC running at 120 MHz.

Thank you for the excellent answer,

Marcus


On 07/03/2017 10:52 AM, Kyeong Su Shin via USRP-users wrote:
> To whom it may concern:
>
> You don't need 160MHz, but that is the filter bandwidth of the
> daughterboard. It WILL give you 160MHz of signal (=120MHz + 40MHz
> worth of aliasing), even if though all you want is 120MHz of bandwidth.
>
> I don't use X3x0 series, so I am not sure what configurable true
> sampling rates are out there, but if you set your sampling rate to
> 160MHz or higher and decimate the data to lower rates using hardware
> decimators in your x310, this problem does not happen (the digital
> decimator will apply low pass filters). That is why you can do 100MS/s
> (sample at 200MS/s -> decimate to 100MS/s).
>
> Regards,
> Kyeong Su Shin
>
> On Mon, Jul 3, 2017 at 1:35 AM, Simon Olvhammar via USRP-users
> <usrp-users at lists.ettus.com <mailto:usrp-users at lists.ettus.com>> wrote:
>
>     Hi,
>
>     I am not sure if I understand correctly.
>     How are the ADC to slow if I use a master clock rate of 120 MHz
>     and sampling rate of 120 MHz on a UBX-160? I don't need 160 MHz
>     bandwidth only 120 MHz.
>
>     Regards
>     Simon
>
>     On 06/28/2017 04:12 PM, Sylvain Munaut wrote:
>
>         Hi,
>
>
>             We currently running a system with a Ettus x310 and a SBX-120.
>             We also a have UBX-160 daughter board.
>
>             For several reasons, mainly due to computer performance
>             limitations, we can
>             only run with a complex sampling rate of 120 MHz.
>             My question is if I will see any improvement in
>             performance, e.g. filter
>             characteristics, if I instead use the UBX-160 and run it
>             at 120 MHz compared
>             to SBX-120 at 120 MHz or are they similar?
>
>         You can't do that.
>
>         If you have the master clock-rate at 120 MHz and use a 160 MHz
>         wide
>         daugtherboard, you will get aliasing because the ADC are too slow.
>         You'd have to go to a 100 MHz samplerate for it to work. (200 MHz
>         sampled by the ADC then HW decimated by 2 to 100 Msps).
>
>         Cheers,
>
>             Sylvain
>
>
>
>     _______________________________________________
>     USRP-users mailing list
>     USRP-users at lists.ettus.com <mailto: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>
>
>
>
>
> _______________________________________________
> USRP-users mailing list
> USRP-users at lists.ettus.com
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/attachments/20170703/d1dbc0c0/attachment-0002.html>


More information about the USRP-users mailing list