Issue with LimeSDR Mini

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Harald Welte laforge at osmocom.org
Fri Jun 4 19:15:01 UTC 2021


Hi Andrew,

On Fri, Jun 04, 2021 at 02:38:06PM +0000, Andrew Back wrote:
> > limesdr mini does not have a onboard-clock which is good (precise)
> > enough for gsm requirements.
> > there is no input which can easily be used with an external source like
> > a gpsdo.
> > thus there is no realistic way to reliably do gsm with the -mini, sorry.
> 
> External clock can be enabled with LimeSDR Mini, but requires moving
> (soldering) a 0R link and then you always have to use external clock.

yes,that is possible.  I tried that, too, some years ago.  The bigger problem,
as far as I recall, are the extremely stringent clock jitter requirements
at this input.  There's no on-board PLL anymore, but it was directly the
sampling clock of the ADC, right?

In any case, at least as I recall, I didn't manage to get a spec
compliant GSM signal out of the LineSDR-mini with that approach using
the clocks I had at my disposal at the time.

But in any case, that jitter / phase noise is mostly a conformance
related topic and  the signal definitely would be good enough to be
properly decoded by commercial UE, particularly in a lab setup with
otherwise near ideal conditions.

Regards,
	Harald
-- 
- Harald Welte <laforge at osmocom.org>            http://laforge.gnumonks.org/
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