Regulatory - Approved antennas list for ESP32-WROOM-32UE

[jgbkhs]

I'm planning on using the ESP32-WROOM-32UE module in a shipping product and plan to leverage the wireless pre-certification status of the module. Typically, this comes with restrictions on which antennas can be used in order to maintain the validity of the pre-certification.

For example here is a table of information for a specific TI wireless module. They do not identify specific part numbers, but many suppliers do go as far as listing exact part numbers:

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I can't find any such approved antennas list in any of the ESP32-WROOM-32UE documentation on the site.
The only mention I can find is in the technical FAQ:

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I have contacted Espressif for this information but have not received a response. Does anyone have any information about these?

[jgbkhs]

Still no reply via the sales contact form. Does anyone have this information?
Can anyone from Espressif reply?

[LindaZhang]

We only measure the gain of PCB antennas and do not measure that of external antennas. Generally, we recommend the maximum gain of external antennas should be smaller than 2.33 dBi.

[jgbkhs]

Thank you Linda. Are you able to provide the test reports or exact antenna(s) used in emissions testing so that we better understand the antenna parameters used?

[jgbkhs]

Linda,

I was able to find the TuV test report for this module under FCC ID 2AC7Z-ESPWROOM32UE, and found that the FCC 15C testing was done with an external PIFA antenna with 4.0dBi of gain, I assume peak.

Farther in the report is an antenna requirement section stating
"According to the manufacturer declared, the EUT has a PIFA antenna, the directional gain of antenna is
4.0 dBi, and the antenna connector is designed with permanent attachment and no consideration of
replacement."

I am assuming if we use an antenna under 4.0dBi peak then we will be fine using the precertification status.

Let me know if you have any other insights or thoughts.

[LindaZhang]

Yes, you can choose an external antenna with a maximum gain smaller than 4.0 dBi.