[USRP-users] Master Clock Supression

devin kelly dwwkelly at gmail.com
Fri Jul 17 15:49:43 EDT 2015


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

On Fri, Jul 17, 2015 at 3:45 PM, devin kelly <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> 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> 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
>>>
>>>  _______________________________________________
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>>>
>>>
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>>>
>>
>>
>> --
>> http://alum.wpi.edu/~dkelly/
>>
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>>
>
>
> --
> http://alum.wpi.edu/~dkelly/
>



-- 
http://alum.wpi.edu/~dkelly/
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