IWR1843: Some question about rlRxGainTempLutData

Hello Bryant,

Thankyou for your concern. 

Let me get back to you on this.

Regards,

Ishita

Hello Bryant, 

I apologize for the delay. Please find my comments below : 

The purpose of calibrations is to ensure the RX gain (and other device related parameters) is maintained as configured by the user despite variations in process and temperature. To achieve this, the internal processor adjusts the mmWave circuit configurations at initialization (to mitigate effects of process variation) and periodically at runtime (to mitigate effects of temperature drifts). 

For this purpose, the device uses RX/TX Look-Up Tables or LUTs. 

The Rx/Tx gain LUT are derived by the firmware based on the Calibration data. This can be read back using the “AWR_RX/TX_GAIN_TEMPLUT_GET_SB” APIs or the user can also override the LUT used by the device by a different set of gain codes. There are specific APIs for this purpose.  

I would recommend you going through the following application note for a better clarification (section : Self-Calibration of mmWave Radar Devices (Rev. A)

Regards,

Ishita

Hello Ishita, 

    Thank you for your reply.

    We find a question,the LUT values obtained by different radar boards are different, and the LUT values obtained by the same radar board are different at different times,why?

    If we set a fixed LUT value, will there be any effect on the chip?

Regards,

Bryant

Hello Bryant, 

The gain of the RX LNA and the TX PA may vary from device to device due to manufacturing process variations, and hence the LUT values may vary from device to device. It also varies across temperature and hence one single device can have different values at different times. As I had mentioned in my previous reply, the LUT values are derived by the firmware based on the Calibration data, so even if the device is at the same temperature at two different times, there might be a only slight variation in the LUT value based on the calibration values.

Gmsy Bryant said:

    If we set a fixed LUT value, will there be any effect on the chip?

Now coming to your next question, calibrations are desired in the device technically to mitigate the effect of process and temperature in order to maintain the gain values programmed by the user, but there is an option to disable the periodic calibrations as well. Please refer to my repsonse in a similar thread linked below : 

(19) IWR1843: The impact of runtime calibration function closure - Sensors forum - Sensors - TI E2E support forums

Regards,

Ishita

Hello Ishita, 

The gain value obtained from the LUT table represents a different meaning each time the power is turned on, even though the LUT values are the same?

Regards,

Bryant

Hello Bryant,

Sorry for the delay. 

I'm not sure if I got your question right. The gain is interpreted as same if the LUT value is same. 

Can you maybe rephrase your question a little?

Regards,

Ishita

Hello，Ishita：

As i said before different device will have different LUT value，and same device will have different lut value every time when device restart.So the LUT value have a uniform standard？Such as one device lut value is 51，another device is also 51，Do these two values correspond to the same thing?

BR

Bryant

Hello Bryant, 

Yes, the meaning of the LUT value is standard. This is explained in the AWR_RX_GAIN_TEMPLUT_SET_SB API as well (see below):

But again as I said, the LUT is generated per device using internal calibrations, based on the process corner of the device and after the profile config API is issued. The LUT value to absolute gain will be a rough conversion. 

I came across a similar thread on this which might interest you : https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/924640/awr1642-awr1642-gain-setting-and-rx-lut-value 

Hope this clarifies things a bit more.

Regards,

Ishita