IWR1443: strange adc data when temperature is ultra low (-40 degree)

The picture above is the normal waveform of raw adc data, zoom fft data and full fft data. When temperature is ultra low(-40 degree), sometimes strange adc data appears as the picture below.  Iwr1443 runs in partial calibration mode, is that might be the reason of this strange phenomenon?

Hi Xiushan

It is likely this is due to partial calibration, as a new calibration would be needed at the lower temperature.

Can you repeat this with the lower temperature performing full calibration?

Also do you observe this behavior while running partial cal at higher temperatures?

Regards,

AG

Hi

This behavior also appears at higher temperature(75 centigrade) and even ordinary temperature, but the frequency is much lower than at -40 centigrade. As to performing full calibration at low temperature, we are going to have a test.

We have two more questions. 1, we need iwr1443 to work stablely under a low energy consumption condition, so the partial calibration mode is still needed. Under what circumstances should we re-run a full calibration to avoid strange adc data? For example, the temperature changes more than 20 degrees or iwr1443 runs more than 30 minutes? 2, if the calibration data is not appropriate for partial calibration, is there a flag that could indicate the status? Or by which way iwr1443 could know that?

Much thanks for your answer.

We perform the full calibration and then run it with partial calibration, this strange wave comes again.

Why the calibration  influense the RF part so much.  

How to lower the influence of the calibration. Such as the smaller band width or smoother chirp or  band width in the center of 77-81?

Our application does not need the RF part very accurate, but we need RF part always works well. How to set the RF part or set the parameter of calibration can achieve it?

We don't need the accuracy of frequency. even don't need the accuracy of chirp. but we need it work and low power.

And we make sure this strange wave has no relationship with the soldering of the chip.

And It seems different version of the software has different probablity of this strange wave.

When partial calibration is performed, is it feasible to select what calibrations to be executed? For example, TX power calibration and/or RX gain calibration and/or IQ mismatch calibration? Besides, we observe that RX gain parameter for iwr1443 also influence the amplitude of the strange adc data, is that a clue to this problem?

Hi Xiushan

Are you saying Full calibration does or does not resolve the phenomenon?

Regards,

AG

Hi Xiushan for these two new questions please open a new thread.

Regards,

AG

Xiushan there is also this Calibration App Note available for reference.

I will be out of office for the next week so for more support please open up a new thread.

After test,  full calibration of every time does resolve the phenomenon. But  at low temperature  full calibration in first time and then running with partial calibration does not resolve the phenomenon. 

Our application is a low power design, so it can not run with full calibration every time.

Hi Xiushan

Understood, thanks for confirming.

I see your new thread here and  I've asked someone to look into it. If it isn't resolved then I will touch base with you on this thread middle of next week.

Regards,

AG