DC Offset vs temperature

Srdjan Milenkovic s.milenkovic at limemicro.com
Fri Jul 27 14:28:08 UTC 2012


Hi Alexander,

As I mentioned before, IQ phase error is quite stable over temperature 
in 900/1800MHz region so let us put it aside. This can be tuned and 
fixed in production.

On the other hand, DC offset and LO leakage are temperature dependent as 
one would expect. However, they can be calibrated in the product as well 
not just in the lab. You need just to trigger built in DC cal blocks and 
optionally use RF loop back to further improve LO leakage. If you want 
to avoid temperature sensor you have an option to do these calibrations 
regularly, every 30min-1h for example. This should track the temperature 
change without having the sensor on board.

Our other customers are using both approaches, with and without 
temperature sensor, depending on application and spec. If they have on 
board temperature sensor they are using it for multiple purpose such as 
monitoring BB, PA, etc.

Best regards, Srdjan

Dr Srdjan Milenkovic

On 26/07/2012 16:48, Alexander Chemeris wrote:
> On Thu, Jul 26, 2012 at 4:37 PM, Alexander Chemeris
> <alexander.chemeris at gmail.com> wrote:
>> On Thu, Jul 26, 2012 at 3:31 PM, Srdjan Milenkovic
>> <s.milenkovic at limemicro.com> wrote:
>>> Combining Thomas's idea of DC recalibration and, if necessary, making
>>> look
>>> up table for IQ phase error correction vs temperature should put us in
>>> good
>>> position to meet the specs.
>> Well, AFAIK, LMS6002D doesn't have a temperature sensor built in and
>> this means we have to install an external one, which again increase
>> BoM cost. Is that's how this issue is solved by your other customers?
>> I wonder is there a way to solve this without introducing a
>> temperature compensation loop.
> Let me clarify - DC offset re-calibration is (more or less) fine in
> lab setup, but it's expensive to manufacture if we have to add
> temperature sensors and put every unit into a temperature camera for
> calibration.
>
> --
> Regards,
> Alexander Chemeris.
> CEO, Fairwaves LLC / ООО УмРадио
> http://fairwaves.ru
>

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