NRF52840QF ANT input impedance

RE: NRF52840QF ANT input impedance

Simonr — Wed, 15 Oct 2025 06:16:34 GMT

I think all information should be in the uploaded file. If you have follow-ups, please take those in the private ticket you made if there's a need for any information to be private.

Best regards,

Simon

RE: NRF52840QF ANT input impedance

Andres Merello — Mon, 13 Oct 2025 19:21:39 GMT

Hi Simon,

Really need this infomration; then, appreciate if you can dig internally or do some measurements at Nordic and share with the community.

Thanks in advance,

Andrés Merello

RE: NRF52840QF ANT input impedance

Simonr — Tue, 07 Oct 2025 11:16:08 GMT

The QFAA matching network and BOM resources available here. I don't have the output impedance exactly as that was provided by another user on DevZone in the case you link to. If you really need it I can try to dig some internally, but can't promise anything.

Best regards,

Simon

RE: NRF52840QF ANT input impedance

Andres Merello — Fri, 03 Oct 2025 21:04:23 GMT

Hi Simon,

Thanks for the quick response.

We are not matching the output of the NRF52840QF to a conventional 50 Ohm load antenna or other standard load, instead is a non standard antenna and this is why we are asking for the output impedance (Zant) seen from the ANT pin. Then we can match to Zant* (the complex conjugate) in order to maximize power transfer to the antenna.

The information that you shared on the NRF52840QI part is what we are asking for the NRF582840QF part: (+) What is the input impedance of nrf52840 in different modes - Nordic Q&A - Nordic DevZone - Nordic DevZone

On the .pdf that you shared, we were not able to find any indication on:

condition of the nRF module i.e. unpowered, Rx mode, Tx mode
in case it was in Tx mode, which was the configured power (understand that the output impedance varies with the configured output power).
if the stray effets (stray capacitances and stray self-inductances) were present on the values of the components present on the schematic.

Sharing the same report as for the aQFN part but for the QF part would be ideal; otherwise, really appreciate if you can share the following information in order of prioirty:

output impedance of the ANT pin in Tx mode at +8dbm
output impedance of the ANT pin in Rx mode

Look forward your response!

Andrés Merello

RE: NRF52840QF ANT input impedance

Simonr — Thu, 02 Oct 2025 08:02:46 GMT

In general, the input impedance is rarely needed, and the load impedance should be what you need. I recommend looking at the nRF52840 reference circuitry for reference.

You can also see this file for more details: devzone.nordicsemi.com/.../nRF52840-QFAA-matching-network-2.pdf

Best regards,

Simon