IWR6843: Output Backoff vs. EIRP

Kouki Yamamoto

Prodigy 20 points

Part Number: IWR6843

Tool/software:

Hi.

The following graph was obtained by connecting an antenna to IWR6843 and varying the output backoff.

The top line shows the set output backoff in hexadecimal, where CH1~3 is the EIRP of Tx channels 1~3.

Calibration is performed at startup, but not on a regular basis.

We recognize that to reduce the EIRP by 1dB, we should reduce the output backoff by -1dB.

There should be a 1dB difference between 0x0b0b0b and 0x0c0c0c, but it is about 4dB lower.

I tried it on several chips with the same result.

What is the cause of the large drop in output power between 0x0b0b0b and 0x0c0c0c?

Also, please let me know how I can lower it by 1dB.

Thank you

9 months ago

0 Ankit Mohanty 9 months ago

TI__Genius 9980 points

Hi Kouki,

Please allow me couple of days' time to check this internally.

Regards

Ankit

0 Ankit Mohanty 9 months ago in reply to Ankit Mohanty

TI__Genius 9980 points

Hi Kouki,

Could you please confirm if boot calibration was performed but not runtime calibration. I would recommend plotting the temperature while plotting the TX EIRP vs TX backoff.

Also, do you see similar behaviour multiple times?

It is recommended to perform.

1. The runtime calibration at the beginning and plot the TX EIRP vs TX backoff along with temperature.

2. The runtime calibration every 10deg.C and plot the TX EIRP vs TX backoff along with temperature.

Regards

Ankit

0 Kouki Yamamoto 9 months ago in reply to Ankit Mohanty

Prodigy 20 points

Thanks for the reply.

Here is the data with temperature taken again today.

The calibration settings have not been changed.

I will measure the data with runtime calibration activated after tomorrow.

Regards

Kouki

0 Kouki Yamamoto 9 months ago in reply to Ankit Mohanty

Prodigy 20 points

Hi Ankit,

I checked with the software designer and the IWR6843 setting when the two data above were measured was “startup, initialization calibration, and runtime calibration only once”.

Does this fall under condition 1 of your suggested conditions?

Regards

Kouki

0 Ankit Mohanty 9 months ago in reply to Kouki Yamamoto

TI__Genius 9980 points

Thanks Kouki Yamamoto,

Yes, this is the first measurement condition. From the temperature also it does not look like a measure shift. We can check once we perform frequent run time calibration.

Regards

Ankit

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IWR6843: Output Backoff vs. EIRP