[USRP-users] Master Clock Supression

Marcus D. Leech mleech at ripnet.com
Fri Jul 17 17:16:35 EDT 2015


On 07/17/2015 03:49 PM, devin kelly via USRP-users wrote:
> Also, I haven't calibrated either unit.  Could that be a factor in 
> this?  While I'm bringing this up, if I do calibrate these, or any 
> other USRPs I have with daughtercards, I run the calibration with all 
> the SMA ports open, right?  No cables, terminators, etc.
>
> Devin
Yeah, just open should work OK.


>
> On Fri, Jul 17, 2015 at 3:45 PM, devin kelly <dwwkelly at gmail.com 
> <mailto:dwwkelly at gmail.com>> wrote:
>
>     I'm not sure what you mean by offset tuning. Is that like just
>     tuning to avoid the tone? Or, is it like the tone might have less
>     power at different frequencies I tune to (like tuning to 3.0505
>     GHz might give me a lower tone-power than 3.5 GHz)?
>
>     Devin
>
>     On Fri, Jul 17, 2015 at 3:15 PM, <mleech at ripnet.com
>     <mailto:mleech at ripnet.com>> wrote:
>
>         Try with offset tuning.  If they're still there, then they are
>         probably actual clock spurs, rather than enhanced LO
>          leakage.
>
>         On 2015-07-17 15:04, devin kelly via USRP-users wrote:
>
>>         Right now I've got two X310s each with two UBXs.  I have each
>>         TX/RX antenna on subdev A connected to each other (with 40 dB
>>         of attenuation), same for each B subdev.  I have all the RX2
>>         antennas terminated.
>>         I see the tones on regardless of the subdev/antenna
>>         combination.  I also tried connecting a spectrum analyzer to
>>         the TX/RX antenna ports and saw no tones.  I also put an
>>         antenna on my spectrum analyzer and saw no tones over the air
>>         with the antenna right next to each X310.
>>         Thanks Again,
>>         Devin
>>
>>         On Fri, Jul 17, 2015 at 11:19 AM, Marcus Müller
>>         <usrp-users at lists.ettus.com
>>         <mailto:usrp-users at lists.ettus.com>> wrote:
>>
>>             Shielding/separation-wise, the X310 should be pretty much
>>             superior in every aspect -- not only is the ADC, DAC,
>>             mixer, amplifier and LO synthesizers in one package on
>>             the B2x0 (the AD9361); the X310 is modular in the sense
>>             that the MCR doesn't even appear to the daugtherboards,
>>             necessarily; it's an FPGA-only clock, generated by the
>>             clock distribution IC on the mainboard, and the UBX,
>>             especially to suppress strong interferers, has a metal
>>             can (which is unique among our RF hardware, so far).
>>             Under that metal can, there's a lot of partitions, which
>>             align with the different jobs and frequency ranges on the
>>             board, compare the schematic [1].
>>
>>             So since you're seeing 200MHz-harmonics, these might
>>             either spuriously get into the antenna ports, or for some
>>             reason, at multiples of 200MHz LO leakage is worse (I
>>             don't expect that). Have you tried using offset tuning
>>             [2] to reduce these spurs?
>>
>>             Best regards,
>>             Marcus
>>
>>
>>             [1] http://files.ettus.com/schematics/ubx/ubx.pdf
>>             [2]
>>             http://files.ettus.com/manual/page_general.html#general_tuning_process
>>
>>
>>
>>             On 17.07.2015 17:03, devin kelly via USRP-users wrote:
>>>             Hello,
>>>             I have an X310 with a UBX daughtercard.  I've noticed
>>>             that there are tones every 200 MHz (I checked 2.4GHx,
>>>             2.6 GHz, 2.8 GHz, 3 GHz, 3.2 GHz).  Do I have any
>>>             options for suppressing the tones?  Is there any
>>>             shielding or RF absorber I can add somewhere?
>>>             The B210s seem to have each section of radio gated off
>>>             (to make it easier to add shielding?).  But  the X310s
>>>             don't as far as I can tell.
>>>             Thanks for any help,
>>>             Devin
>>>
>>>             _______________________________________________
>>>             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
>>
>>             _______________________________________________
>>             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://alum.wpi.edu/~dkelly/ <http://alum.wpi.edu/%7Edkelly/>
>>
>>         _______________________________________________
>>         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://alum.wpi.edu/~dkelly/ <http://alum.wpi.edu/%7Edkelly/>
>
>
>
>
> -- 
> http://alum.wpi.edu/~dkelly/ <http://alum.wpi.edu/%7Edkelly/>
>
>
> _______________________________________________
> 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/20150717/10f04805/attachment-0002.html>


More information about the USRP-users mailing list