[USRP-users] Master Clock Supression

Marcus Müller marcus.mueller at ettus.com
Fri Jul 17 11:19:14 EDT 2015


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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> USRP-users at lists.ettus.com
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