Improving LMS6002 phase noise

Alexander Chemeris alexander.chemeris at gmail.com
Sun Jul 22 14:16:56 UTC 2012


On Sun, Jul 22, 2012 at 3:11 PM, Srdjan Milenkovic
<s.milenkovic at limemicro.com> wrote:
> On 21/07/2012 16:28, Alexander Chemeris wrote:
>>
>> Hi Srdjan,
>>
>> On Sat, Jul 21, 2012 at 4:33 PM, Srdjan Milenkovic
>> <s.milenkovic at limemicro.com> wrote:
>>>
>>> Hi all,
>>>
>>> As far as I am aware, you are currently discussing how to improve LMS6002
>>> PLL phase noise. Below are some inputs from my side which may help.
>>
>> Yes, here are some pictures of phase noise we have at UmTRX right now:
>> http://lists.osmocom.org/pipermail/umtrx/2012-July/000030.html
>>
>> It looks like they're 5-12dB higher then data I saw in your
>> temperature measurement report. First thought is that this could be
>> due to a clock source. Did you use your EVB board for those
>> measurements?
>
> Yes, we used Lime EVB, 30.72MHz TCXCO. However, using 26MHz instead of
> 30.72MHz TCXCO should not affect phase noise so much (5-12dB). Do you have
> an alternative 26MHz TCXCO with better PN? As you quite rightly mentioned,
> you are probably limited by TCXCO PN at the moment.

Could you please share LMS configuration you used during this test, so
we could re-create it locally with the EVB we have. A full register
dump of the chip would be ideal.

-- 
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru




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