LMS TxLO noise

Alexander Chemeris alexander.chemeris at gmail.com
Sat Jul 21 07:51:06 UTC 2012


On Sat, Jul 21, 2012 at 7:03 AM, Thomas Tsou <thomastsou at gmail.com> wrote:
> I tried calibrating LO leakage cancellation again and found out that
> it wasn't calibrated enough. The settings are very sensitive and
> increasing the I and Q shifts by one made a large difference on the
> E4406.

This is my experience as well. Near the optimum point even change of
calibration registers by 1 makes big difference. When you're far off,
a change of a calibration register could be almost unnoticeable.

I've started adding notes about LMS calibration here:
http://code.google.com/p/umtrx/wiki/LMS6002DCalibration
Please write down there all useful notes about all types of
calibration we're doing.

> The RSA seems to compensate, though, because the same changes
> don't affect it at all.

How could it compensate? For RSA it should look like a genuine sine signal.

> I also tried some different frequencies. At the not useful frequency
> of 240 MHz, we are not far from target values. At 945 MHz, it is
> better than before, but still too high. The 1900 MHz band is not so
> good.

Well, we're more interested in GSM900, but this clearly shows that
there is an issue with the LMS PLL noise.


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




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