Improving LMS6002 phase noise

Alexander Chemeris alexander.chemeris at gmail.com
Sun Jul 22 11:16:43 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.

We'll look for a one. UmTRX has Clock In connector, so it should not
be an issue to feed it with an other clock source.

Btw, for everyone's reference, the aforementioned document with LMS
performance measurements is now published here:
https://github.com/chemeris/lms6002-documentation/blob/master/LMS6002D-Temperature%20testing%20July%202011.pdf

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




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