NRF52840QF ANT input impedance

[Andres Merello]

We are using part nRF52840QF (QFN package, not aQFN) as part of new designs as it has the following improvements compared with the nRF52832:

• Output power of +8dbm
• Extended range availability

 

I am writing in reference to the input impedance in order to implement the matching network between the nRF52840QF and our antenna.

We were able to find on the Nordic’s DevZone this information for the aQFN package, but not for the QFN one. Please, find the report attached. Link: What is the input impedance of nrf52840 in different modes - Nordic Q&A - Nordic DevZone - Nordic DevZone

 

Could you please provide this information for the QFN package?

[Simonr]

Hi

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: nRF52840 QFAA matching network 2.pdf

Best regards,

Simon

[Andres Merello]

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