Multiplexing 6 Antennas with a Single NFC Reader (e.g., ST25R3916B) — Best Practice?

[MERSI]

Hi everyone,

I'm working on a project that requires multiplexing 6 NFC antennas to a single NFC reader, such as the ST25R3916B. From my understanding, because the reader uses separate RFOx (TX) and RFIx (RX) lines for differential communication, I need to multiplex both RFOx and RFIx for each antenna.

The most cost-efficient and compact approach I can currently think of looks like this:
STM32 + ST25R3916B (RFOx/RFIx)
--> Matching Network
--> RF MUX
--> [optional EMC Filter]
--> Antenna

Alternatively, if I place the matching network after the multiplexer like this:
STM32 + ST25R3916B (RFOx/RFIx)
--> RF MUX
--> Matching Network
--> [optional EMC Filter]
--> Antenna

…then I would need two separate MUXes per antenna path (one for RFO, one for RFI), effectively doubling the number of switches, which significantly increases both cost and board space.

My questions:

• Has anyone implemented method 1 (matching network before the MUX)?

• Are there known issues (e.g., detuning, crosstalk, or signal loss)?

• Are there better or more efficient ways to multiplex multiple antennas with differential TX/RX lines?

• Do you have any recommendations?

Thanks a lot in advance for any suggestions or shared experiences!

Best regards

[Travis Palmer]

Hi Mersi,

Is this different to your previous question in the community?

ST has just released an Application note which should fit your need. 

Please have a look at https://www.st.com/content/st_com/en/search.html#q=an6121-t=resources-page=1

In case of questions, please let us know.

br Travis

[Travis Palmer]

Hi Mersi,

there did a mistake happen with Figure-7.

below the correct one.

BR Travis