IWR6843AOP: How to set the txOutPower for FCC compliance?

Parthipan Siva

Part Number: IWR6843AOP
Other Parts Discussed in Thread: AWR1642, IWR6843

Hi,

We are currently going through testing for FCC certification of a product using IWR6843AOP. Our test house informed us in the current configuration:

[they] got the power measurements of your device:

EIRP = 15.057 dBm

Conducted Output Power = 10.057 dBm

Your device is within the 57 to 71 GHz with a bandwidth of 4 GHz, which means the limits are:

EIRP = 10 dBm

Conducted Output Power = -10 dBm

We are using the full 4GHz bandwidth and to meet the conducted output power of -10dB we need <txOutPower> to be at least 20 (test house is computing conducted output power as EIRP-5dB, where 5dB is antenna gain on IWR6843AOP). Based on https://e2e.ti.com/support/sensors-group/sensors/f/sensors-forum/633604/awr1642-about-setting-tx-output-power-back-off-code-for-tx-antennas we can use 24 or 30.

Questions:

1) is the valid values of <txOutPower> for IWR6843 same as the AWR1642? Above forum post stated valid values are [0,1,2,3,4,5,6,12,18,24,30]

2) What was the value of the <txOutPower> used, in the 4GHz bandwidth scenario, to obtain FCC certification for the IWR6843AOP EVM as listed here https://dev.ti.com/tirex/explore/node?a=VLyFKFf__4.9.0&devtools=IWR6843AOPEVM&node=A__AH74gbVaGPlKZnkAX0BpAA__com.ti.mmwave_industrial_toolbox__VLyFKFf__4.9.0 ?

Cheers

over 2 years ago

0 Nathan Block over 2 years ago

TI__Mastermind 37805 points

Parthipan Siva said:
1) is the valid values of <txOutPower> for IWR6843 same as the AWR1642? Above forum post stated valid values are [0,1,2,3,4,5,6,12,18,24,30]

The ICD says that it's supported in steps of 3 dB.

Parthipan Siva said:
2) What was the value of the <txOutPower> used, in the 4GHz bandwidth scenario, to obtain FCC certification for the IWR6843AOP EVM as listed here https://dev.ti.com/tirex/explore/node?a=VLyFKFf__4.9.0&devtools=IWR6843AOPEVM&node=A__AH74gbVaGPlKZnkAX0BpAA__com.ti.mmwave_industrial_toolbox__VLyFKFf__4.9.0 ?

I would imagine it would be 24 = 0x18, just based off the fact that the conducted emission must be below -10 dBm, which indicates that the backoff value would need to be 22 dB below the maximum value of 12 dBm to get to -10 dBm, which makes -24 dB the highest possible option. I will see if we can verify this.

Best,

Nate

0 Parthipan Siva over 2 years ago in reply to Nathan Block

Prodigy 160 points

Thanks Nate.

If you can verify the value used for FCC lab tests of the EVM I would greatly appreciate it. I do agree -24 dB makes sense but if you look at the Table 7.3-2 in (https://dev.ti.com/tirex/explore/node?a=VLyFKFf__4.9.0&devtools=IWR6843AOPEVM&node=A__AH74gbVaGPlKZnkAX0BpAA__com.ti.mmwave_industrial_toolbox__VLyFKFf__4.9.0) you see that for 4Ghz bandwidth the measured EIRP is around -18dB which seems to indicate maybe -30dB backoff was used. If -30dB was used, was -30dB needed to pass FCC tests or just happened to be the value that was decided to be used.

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IWR6843AOP: How to set the txOutPower for FCC compliance?