IWR1843: Target Sensitivity Fluctuation

Hello.

We are looking into this and will provide an update by the end of day tomorrow.

Sincerely,

Santosh

Hi Yasuaki,

Could you please elaborate on the "certain target" that is used for detection. Also, could you please specify if the "amplitude of the RF received waveform (ADC buffer data) fluctuates by about 2dB" is the RF Gain Target fluctuation or RX Gain fluctuation.

AWR1243: What's different between RX Gain and RF Gain Target? - Sensors forum - Sensors - TI E2E support forums

There might be +-2dB variation for TX Output Power and RX Gain for the device.

Regards

Ankit

Hi Ankit, 
Thank you for your reply.

We are examining sensitivity variations in an environment where a metal reflector (10m^2) is positioned at a distance of 1.3m from the radar, with respect to a "certain target."
It was unclear whether the variations pertain to "RF Gain Target" or "RX Gain" after reviewing the provided URL, as the information was difficult to understand.
[Question 1] I will explain the details below; based on this information, can you determine whether the variation is related to "RF Gain Target" or "RX Gain"?

• The "amplitude of the RF received waveform (ADC buffer data)" refers to waveform data stored in the DSS_ADCBUF Buffer (address 0x5200 0000). Upon inspecting the ADC buffer data, as shown in Graph 2, the two data points that had a 2dB variation showed approximately a 2dB difference in the amplitude of the ADC buffer data. (The data in Graph 2 was measured in an environment without reflections from other targets. The sensitivity difference in Graph 2 is a rough estimate based on manual calculation, whereas Graph 1 extracts the target sensitivity from the FFT results of the ADC buffer data.)
• Both "RF Gain Target" and "RX Gain" in the profile settings have been set to 30dB.
  (rlProfileCfg_t.rxGain=RL_RX_GAIN_30_dB(0x1EU))

It has been indicated that there might be a ±2dB variation in TX output power and RX gain, but we believe that the RX gain is the contributing factor.
[Question 2] Does the RX gain change according to the results of the Self Calibration described in document SPRACF4A?

[Question 3] If the answer to Question 2 is Yes, are there any external factors other than temperature and boot time RX Gain results that would affect the Self Calibration results of the RX gain? If so, what are they?

[Question 4] Is temperature the only information newly measured during the run time calibration of RX gain? If there are others, what are they?

[Question 5] Can the CAL information related to the RX gain be read using mmWaveSDK's rlRfCalibDataStore() and rlRxGainTempLutGet()? Also, are there any other functions to extract information related to the RX gain?

[Question 6] Can the Self Calibration of the RX gain (including boot time calibration) be omitted by setting the MMWave_CalibrationCfg.chirpCalibrationCfg.enableCalibration in the MMWave_start() structure argument to false?

Best regards,
Yasuaki

Hello.

Let me look into this and provide an update for you by the end of the day tomorrow.

Sincerely,

Santosh

Apologies for the delay in response.  I am still looking into this and will have an update by the end of the day Monday.

Sincerely,

Santosh

Hello.

How is the investigation going?
If there are any questions you can answer, please respond to them first.

Best regards,
Yasuaki

Hello.

I have reviewed the "mmWave Radar Interface Control Document."
I found that the LSB of the RX gain temperature LUT is set in 2dB steps.
I am considering whether this could be the cause of the issue.

[Question 7] When is the RX gain temperature LUT updated? Please answer for each of the following scenarios:

• At power ON?
• Upon execution of MMWave_open()?
• During Runtime Calibration?
• Other?

Best regards, 
Yasuaki

Hello.

Apologies for the delay in response.

yasuaki oda said:

[Question 2] Does the RX gain change according to the results of the Self Calibration described in document SPRACF4A?

No, Rx gain is set as part of the factory calibration configuration command.

yasuaki oda said:

[Question 4] Is temperature the only information newly measured during the run time calibration of RX gain? If there are others, what are they?

Based on the calibration that is being run at runtime, it can be temperature or some other analog measurement required for that specific calibration.  Please refer to the document on self-calibrations to understand what calibrations can be executed at runtime and what measurements it might take.

yasuaki oda said:

[Question 6] Can the Self Calibration of the RX gain (including boot time calibration) be omitted by setting the MMWave_CalibrationCfg.chirpCalibrationCfg.enableCalibration in the MMWave_start() structure argument to false?

It is set to false by default when the default calibration configuration is set during MmwDemo_startSensor().

yasuaki oda said:

[Question 5] Can the CAL information related to the RX gain be read using mmWaveSDK's rlRfCalibDataStore() and rlRxGainTempLutGet()? Also, are there any other functions to extract information related to the RX gain?

You can use the rl_fecssRfRxTxCalDataGet to get the struct that contains information include the Rx Gain Codes LUT.

I am still looking into questions 1 and 7, and will have an update by the end of the day Monday.

Sincerely,

Santosh

Hello, 
Thank you for your reply.

We have reviewed the document Self-Calibration (SPRACF4C). It appears that several calibrations, including RX Gain, are recommended to be conducted at the factory.
[Question 8] Regarding products that use the method of reading out the LUT created in the factory during In-Field Operation, is it okay to continue using that LUT for a long time, such as 10 years? For example, is there a possibility that the RX Gain might change due to the LUT not being updated?

Best regards,
Yasuaki

Hello,

We have extracted the RX Gain LUT and investigated its relationship with the target sensitivity.
It has been found that the target sensitivity tends to vary by 2dB in accordance with changes in the RX RF Gain Code.
We have grasped the approximate trend of the MMIC temperature and the RX Gain LUT values that are likely being used,
but the specific method for selecting LUT values is unclear.
[Question 9] How are the 10 temperature sensors within the IWR1843 used during In-Field Operation to select the RX Gain LUT value?
(Is it based on the temperature of a single sensor, or perhaps on the maximum or average values?)

I have a question regarding calibration in the factory.
[Question 10] Could you please explain how to achieve stable calibration results in the factory?
(I understand that avoiding interference waves is as described in the "Self-Calibration" document.
Would actions such as warming up the MMIC be necessary?)

Could you please provide answers to Questions 7 through 10 by this Wednesday?
Alternatively, by when could you provide the answers?

Best regards,
Yasuaki

Hello.

Apologies for the delay in response as I was out of office this past week.  Let me look into these and have a response by the end of the week.

Sincerely,

Santosh

Hello Yasuaki.

Please see my responses below.

yasuaki oda said:

[Question 7] When is the RX gain temperature LUT updated? Please answer for each of the following scenarios:

• At power ON?
• Upon execution of MMWave_open()?
• During Runtime Calibration?
• Other?

I believe this is done at boot time, as explained in the self-calibration application note.

yasuaki oda said:

[Question 8] Regarding products that use the method of reading out the LUT created in the factory during In-Field Operation, is it okay to continue using that LUT for a long time, such as 10 years? For example, is there a possibility that the RX Gain might change due to the LUT not being updated?

I am still looking into this one, I will have an update by the end of the day Tuesday.

yasuaki oda said:

[Question 9] How are the 10 temperature sensors within the IWR1843 used during In-Field Operation to select the RX Gain LUT value?
(Is it based on the temperature of a single sensor, or perhaps on the maximum or average values?)

According to the self-calibration application note, "The measured temperature at the time of calibration (this is the average of the temperature sensor readings from the temperature sensors located near the TX and RX channels)."

yasuaki oda said:

[Question 10] Could you please explain how to achieve stable calibration results in the factory?

For information on production testing, please refer to the document linked here.

Sincerely,

Santosh

Hello, 
Thank you for your reply.

I would like to know more about the Runtime Calibration of RX Gain.
[Question 11]
Is the Runtime Calibration of RX Gain only conducted with temperature and LUT-based sensitivity correction in 2dB steps?
Are there any additional RX Gain calibration algorithms for Rx Gain?

Best regards,
Yasuaki

Hello.

i don't believe there are.  For new questions please submit a new post to the forum as the questions are starting to deviate from the original query.

Sincerely,

Santosh